{"id":17530,"date":"2026-09-09T13:40:58","date_gmt":"2026-09-09T05:40:58","guid":{"rendered":"https:\/\/www.wehopower.com\/?post_type=news&#038;p=17530"},"modified":"2026-09-09T13:40:58","modified_gmt":"2026-09-09T05:40:58","slug":"power-supply-hold-up-time-test","status":"publish","type":"news","link":"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/","title":{"rendered":"How to Test Power-Supply Hold-Up Time Before Specifying a DC UPS"},"content":{"rendered":"<style class=\"weho-daily-article-style\">\n<p>    .weho-daily-article{\n      --ink:#172747;\n      --muted:#526884;\n      --cobalt:#284bd6;\n      --cobalt-dark:#173aaf;\n      --magenta:#c9218b;\n      --magenta-dark:#8c185f;\n      --ice:#eaf7ff;\n      --ice-2:#f6fbff;\n      --mint:#e8faf5;\n      --green:#12684f;\n      --line:#c9ddf1;\n      --white:#ffffff;\n      --shadow:0 24px 70px rgba(32,73,132,.12);\n    }\n    .weho-daily-article, .weho-daily-article *{box-sizing:border-box}\n    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19px;border-radius:10px;background:var(--cobalt);color:#fff;text-decoration:none;font-weight:800}\n    .weho-daily-article .footer{padding:24px 7%;background:#f2f9ff;border-top:1px solid var(--line);color:var(--muted);font-size:12px}\n    @media(max-width:820px){\n      .weho-daily-article .page{width:100%;margin:0}\n      .weho-daily-article .hero,.weho-daily-article main{border-radius:0;border-left:0;border-right:0;box-shadow:none}\n      .weho-daily-article .hero{padding:48px 22px 36px}\n      .weho-daily-article .hero:after{font-size:100px;right:-10px}\n      .weho-daily-article .decision-strip,.weho-daily-article .outcomes,.weho-daily-article .boundary,.weho-daily-article .records{grid-template-columns:1fr}\n      .weho-daily-article .content{padding:38px 22px 55px}\n      .weho-daily-article section:before{position:static;display:block;margin-bottom:10px}\n      .weho-daily-article .stage{padding:75px 21px 24px}\n      .weho-daily-article .stage:before{left:21px;top:20px}\n      .weho-daily-article figure{margin-left:-22px;margin-right:-22px}\n      .weho-daily-article figure img{border-radius:0;border-left:0;border-right:0}\n      .weho-daily-article figcaption{padding:0 22px}\n      .weho-daily-article h1{font-size:41px}\n    }\n    @media print{\n      .weho-daily-article{background:#fff}\n      .weho-daily-article .preview{display:none}\n      .weho-daily-article .page{width:100%;margin:0}\n      .weho-daily-article .hero,.weho-daily-article main{box-shadow:none;border-radius:0}\n      .weho-daily-article a{color:var(--ink)}\n    }<\/p>\n<\/style>\n<div class=\"weho-daily-article\" data-weho-package=\"weho-20260909-a03\" data-weho-version=\"1.0.0\" data-design=\"cobalt-threshold-lab-record\">\n<div class=\"weho-current-layout\">\n<div class=\"page\">\n<header class=\"hero\">\n<div class=\"hero-copy\">\n<div class=\"eyebrow\">WEHO technical decision record \u00b7 hold-up go\/no-go<\/div>\n<p class=\"dek\">Define the load&#8217;s minimum valid voltage, measure threshold-crossing time under an approved interruption, and decide whether the existing AC-DC supply bridges the event\u2014or whether a continuity gap remains.<\/p>\n<div class=\"decision-strip\" aria-label=\"Article scope\">\n<div><strong>Threshold<\/strong>Vmin at the named load terminals<\/div>\n<div><strong>Comparison<\/strong>t_measured vs. t_required + allowance<\/div>\n<div class=\"gap\"><strong>Boundary<\/strong>No battery Ah or UPS runtime sizing<\/div><\/div><\/div>\n<\/header>\n<p>    <main><\/p>\n<div class=\"content\">\n<div class=\"lead\">\n<p><strong>Direct answer:<\/strong> define the load-terminal minimum valid voltage, the approved input interruption, the actual load, the environment, and the exact power-supply sample before asking whether a DC UPS is necessary. A qualified laboratory can then create the approved interruption with controlled equipment and measure the time from the input-loss event to the first crossing below that voltage threshold. Compare the shortest valid measured time with the required ride-through time plus an agreed measurement allowance.<\/p>\n<div class=\"outcomes\">\n<div class=\"outcome\"><b>PSU bridges<\/b>Every accepted record stays above the load&#8217;s approved minimum voltage for the required interval plus allowance, under the recorded conditions.<\/div>\n<div class=\"outcome gap\"><b>Gap remains\u2014evaluate UPS<\/b>The evidence does not meet that rule, or the test conditions do not cover the application.<\/div><\/div>\n<p>Neither result proves universal performance. \u201cPSU bridges\u201d applies only to the named model and revision, sample population, input condition, measured load state, ambient condition, threshold, interruption profile, instrumentation, and acceptance rule. \u201cEvaluate UPS\u201d starts a different engineering task; it is not permission to guess a battery capacity or backup runtime.<\/p>\n<\/p><\/div>\n<figure>\n          <img fetchpriority=\"high\" src=\"https:\/\/i1.wp.com\/www.wehopower.com\/wp-content\/uploads\/2026\/09\/weho-power-supply-hold-up-time-test-hero-0c3f65926cca.webp?quality=85&strip=all\" alt=\"How to Test Power-Supply Hold-Up Time Before Specifying a DC UPS  title=\" width=\"1440\" height=\"810\" loading=\"eager\" fetchpriority=\"high\" decoding=\"async\" How to Test Power-Supply Hold-Up Time Before Specifying DC UPS title=\"\"><figcaption>AI-generated editorial concept. It is not a WEHO product, approved wiring diagram, customer installation, live test, measured waveform, or performance result. The apparatus and inactive instrument displays are illustrative only.<\/figcaption><\/figure>\n<section id=\"interruption-contract\" data-step=\"01 \/ CONTRACT\">\n<div id=\"ez-toc-container\" class=\"ez-toc-v2_0_86 counter-hierarchy ez-toc-counter ez-toc-grey ez-toc-container-direction\">\n<div class=\"ez-toc-title-container\">\n<p class=\"ez-toc-title\" style=\"cursor:inherit\">Table of Contents<\/p>\n<span class=\"ez-toc-title-toggle\"><a href=\"#\" class=\"ez-toc-pull-right ez-toc-btn ez-toc-btn-xs ez-toc-btn-default ez-toc-toggle\" aria-label=\"Toggle Table of Content\"><span class=\"ez-toc-js-icon-con\"><span class=\"\"><span class=\"eztoc-hide\" style=\"display:none;\">Toggle<\/span><span class=\"ez-toc-icon-toggle-span\"><svg style=\"fill: #999;color:#999\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" class=\"list-377408\" width=\"20px\" height=\"20px\" viewBox=\"0 0 24 24\" fill=\"none\"><path d=\"M6 6H4v2h2V6zm14 0H8v2h12V6zM4 11h2v2H4v-2zm16 0H8v2h12v-2zM4 16h2v2H4v-2zm16 0H8v2h12v-2z\" fill=\"currentColor\"><\/path><\/svg><svg style=\"fill: #999;color:#999\" class=\"arrow-unsorted-368013\" xmlns=\"http:\/\/www.w3.org\/2000\/svg\" width=\"10px\" height=\"10px\" viewBox=\"0 0 24 24\" version=\"1.2\" baseProfile=\"tiny\"><path d=\"M18.2 9.3l-6.2-6.3-6.2 6.3c-.2.2-.3.4-.3.7s.1.5.3.7c.2.2.4.3.7.3h11c.3 0 .5-.1.7-.3.2-.2.3-.5.3-.7s-.1-.5-.3-.7zM5.8 14.7l6.2 6.3 6.2-6.3c.2-.2.3-.5.3-.7s-.1-.5-.3-.7c-.2-.2-.4-.3-.7-.3h-11c-.3 0-.5.1-.7.3-.2.2-.3.5-.3.7s.1.5.3.7z\"\/><\/svg><\/span><\/span><\/span><\/a><\/span><\/div>\n<nav><ul class='ez-toc-list ez-toc-list-level-1 ' ><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-1\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#Start_with_an_interruption_contract_not_a_catalog_number\" >Start with an interruption contract, not a catalog number<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-2\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#Keep_three_time_questions_separate\" >Keep three time questions separate<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-3\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#Ride-through\" >Ride-through<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-4\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#Output_discharge\" >Output discharge<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-5\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#UPS_backup\" >UPS backup<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-6\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#Put_a_laboratory_authorization_gate_before_any_measurement\" >Put a laboratory authorization gate before any measurement<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-7\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#This_is_not_a_mains_connection_procedure\" >This is not a mains connection procedure<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-8\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#Run_a_six-stage_evidence_protocol\" >Run a six-stage evidence protocol<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-9\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#Freeze_the_specimen_and_configuration\" >Freeze the specimen and configuration<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-10\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#Approve_the_interruption_matrix\" >Approve the interruption matrix<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-11\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#Establish_a_stable_baseline\" >Establish a stable baseline<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-12\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#Capture_synchronized_event_evidence\" >Capture synchronized event evidence<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-13\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#Reduce_each_valid_record_consistently\" >Reduce each valid record consistently<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-14\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#Repeat_recover_and_sign\" >Repeat, recover and sign<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-15\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#Apply_one_conservative_decision_rule\" >Apply one conservative decision rule<\/a><ul class='ez-toc-list-level-3' ><li class='ez-toc-heading-level-3'><a class=\"ez-toc-link ez-toc-heading-16\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#Explicitly_hypothetical_threshold_example\" >Explicitly hypothetical threshold example<\/a><\/li><\/ul><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-17\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#Read_published_product_rows_as_leads_not_verdicts\" >Read published product rows as leads, not verdicts<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-18\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#If_a_gap_remains_open_a_new_UPS_decision\" >If a gap remains, open a new UPS decision<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-19\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#Issue_a_decision_record_that_procurement_can_audit\" >Issue a decision record that procurement can audit<\/a><\/li><li class='ez-toc-page-1 ez-toc-heading-level-2'><a class=\"ez-toc-link ez-toc-heading-20\" href=\"https:\/\/www.wehopower.com\/fa\/news\/power-supply-hold-up-time-test\/#Prepare_the_evidence_before_requesting_a_model_review\" >Prepare the evidence before requesting a model review<\/a><\/li><\/ul><\/nav><\/div>\n<h2><span class=\"ez-toc-section\" id=\"Start_with_an_interruption_contract_not_a_catalog_number\"><\/span>Start with an interruption contract, not a catalog number<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>A hold-up-time number has meaning only when its threshold and operating conditions travel with it. For this protocol, <strong>hold-up time<\/strong> is the interval from the laboratory&#8217;s defined input-interruption event to the first time the voltage at the specified load terminals falls below the load&#8217;s approved minimum valid voltage, <strong>Vmin<\/strong>.<\/p>\n<p>That definition is an application decision boundary. The load\u2014not the power-supply marketing name\u2014sets Vmin. It may come from an approved equipment specification, an undervoltage-lockout characterization, or a system acceptance limit. If no controlled source establishes Vmin, the hold-up test cannot produce a defensible pass\/fail decision.<\/p>\n<p>Freeze the following fields before test authorization:<\/p>\n<div class=\"table-wrap\">\n<table>\n<thead>\n<tr>\n<th>Contract field<\/th>\n<th>What the approved record must contain<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td>Load boundary<\/td>\n<td>Exact terminals where voltage validity matters; include production cable, connector, protection and distribution elements when they are inside the decision boundary<\/td>\n<\/tr>\n<tr>\n<td>Vmin<\/td>\n<td>Approved minimum load-terminal voltage, its source, revision and any duration qualification<\/td>\n<\/tr>\n<tr>\n<td>Required interruption<\/td>\n<td>Duration and approved shape or source profile; nominal input alone is insufficient<\/td>\n<\/tr>\n<tr>\n<td>Input condition<\/td>\n<td>Voltage, frequency where applicable, tolerance and the defined event used as time zero<\/td>\n<\/tr>\n<tr>\n<td>Load state<\/td>\n<td>Measured steady and dynamic current or power during the interruption; identify startup, transmit, actuator or processor states<\/td>\n<\/tr>\n<tr>\n<td>Environment<\/td>\n<td>Ambient temperature, airflow, mounting and warm-up condition relevant to the test<\/td>\n<\/tr>\n<tr>\n<td>Specimen<\/td>\n<td>Exact model, output variant, hardware or document revision, serial\/sample ID and adjustment setting<\/td>\n<\/tr>\n<tr>\n<td>Measurement rule<\/td>\n<td>Instrument IDs, bandwidth\/sample settings selected by the lab, time-reference definition, repeat count, uncertainty or allowance and invalid-run criteria<\/td>\n<\/tr>\n<\/tbody>\n<\/table><\/div>\n<p>Do not replace measured load with the nameplate maximum unless the project has formally chosen that as the acceptance condition. Do not replace a defined interruption with \u201cbrief outage.\u201d The purpose of the contract is to make two laboratories interpret the question the same way.<\/p>\n<p><a href=\"https:\/\/products.pulspower.com\/sg\/mwdownloads\/download\/link\/id\/3059\/\" rel=\"noopener\" target=\"_blank\">PULS product documentation<\/a> provides a useful public example of why conditions matter: it defines hold-up behavior and presents different hold-up values at different load levels. That example does not transfer a PULS result to a WEHO model, but it supports the discipline of attaching load and input conditions to every hold-up claim.<\/p>\n<\/section>\n<section id=\"three-time-questions\" data-step=\"02 \/ BOUNDARY\">\n<h2><span class=\"ez-toc-section\" id=\"Keep_three_time_questions_separate\"><\/span>Keep three time questions separate<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>The same AC-removal event can start several clocks, but the buyer tasks are different.<\/p>\n<div class=\"boundary\">\n<article>\n<h3><span class=\"ez-toc-section\" id=\"Ride-through\"><\/span>Ride-through<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>How long the powered load remains at or above Vmin during a temporary approved input interruption. It ends at the first Vmin crossing and supports this article&#8217;s two outcomes.<\/p>\n<\/article>\n<article>\n<h3><span class=\"ez-toc-section\" id=\"Output_discharge\"><\/span>Output discharge<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>How long residual output energy takes to decay after intentional shutdown. It governs shutdown waiting and access controls. This article provides no safe-discharge interval.<\/p>\n<\/article>\n<article>\n<h3><span class=\"ez-toc-section\" id=\"UPS_backup\"><\/span>UPS backup<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>How a continuity system transfers, supports load and charging, manages a battery, signals events, recovers and meets a service-runtime objective.<\/p>\n<\/article><\/div>\n<p>A load staying valid for 20 ms says nothing about when a primary circuit or internal capacitor becomes safe to touch. Likewise, a hold-up test does not calculate battery ampere-hours and does not validate a UPS. This separation prevents an attractive but unsafe shortcut: turning a published \u201chold-up\u201d cell into a promise of seamless transfer or minutes of battery service.<\/p>\n<\/section>\n<section id=\"authorization-gate\" data-step=\"03 \/ SAFETY GATE\">\n<h2><span class=\"ez-toc-section\" id=\"Put_a_laboratory_authorization_gate_before_any_measurement\"><\/span>Put a laboratory authorization gate before any measurement<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<div class=\"safety\">\n<h3><span class=\"ez-toc-section\" id=\"This_is_not_a_mains_connection_procedure\"><\/span>This is not a mains connection procedure<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Input interruption testing can expose hazardous energy, high inrush current, stored charge and instrument-grounding hazards. A <strong>qualified laboratory<\/strong> must own the hazard analysis, approved schematic, protective enclosure, equipment ratings, interlocks, emergency response, connection method and stop limits.<\/p>\n<\/p><\/div>\n<p>The lab may select a rated programmable AC source or other controlled interruption apparatus, a representative load, and suitable isolated or differential measurement equipment. <a href=\"https:\/\/www.keysight.com\/zz\/en\/assets\/7018-03636\/application-notes\/5991-1117.pdf\" rel=\"noopener\" target=\"_blank\">Keysight&#8217;s official switching-power-supply measurement material<\/a> shows the legitimate scope of oscilloscope-based time-domain characterization. It does not authorize a universal connection arrangement, so no probe placement or mains connection is derived from it here.<\/p>\n<p>The authorization gate must reject:<\/p>\n<ul>\n<li>improvised live-mains switching or exposed primary-side work;<\/li>\n<li>opening the supply or probing internal primary circuits;<\/li>\n<li>defeating protective earth, floating a protective-earth oscilloscope, or placing a grounded probe clip on an uncertain node;<\/li>\n<li>bypassing fuses, covers, interlocks, current limits or other protections;<\/li>\n<li>unapproved battery connections, battery shorts, reverse polarity or improvised charging;<\/li>\n<li>a test plan without rated apparatus, stop criteria, specimen containment and a responsible qualified person.<\/li>\n<\/ul>\n<p>Only the externally accessible measurement points and method approved for that exact setup belong in the laboratory procedure. If the source, load or instrument cannot safely create and capture the specified event, the result is <strong>HOLD\u2014method not authorized<\/strong>, not an estimated hold-up time.<\/p>\n<\/section>\n<section id=\"evidence-protocol\" data-step=\"04 \/ PROTOCOL\">\n<h2><span class=\"ez-toc-section\" id=\"Run_a_six-stage_evidence_protocol\"><\/span>Run a six-stage evidence protocol<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<div class=\"protocol\">\n<article class=\"stage\">\n<h3><span class=\"ez-toc-section\" id=\"Freeze_the_specimen_and_configuration\"><\/span>Freeze the specimen and configuration<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Photograph or otherwise identify the label and record the exact output variant, adjustment, revision and sample ID. Record all elements between the supply output and the load measurement boundary. A bench result taken directly at supply terminals may not represent the voltage at a remote controller after cable and connector drop.<\/p>\n<p>Do not mix samples, revisions or output variants in one summary value. If procurement needs a production claim, engineering must define the number of samples and lot coverage rather than treating one unit as universal evidence.<\/p>\n<\/article>\n<article class=\"stage\">\n<h3><span class=\"ez-toc-section\" id=\"Approve_the_interruption_matrix\"><\/span>Approve the interruption matrix<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>List the interruption cases the application actually requires. Each row should name the starting input, interruption duration\/profile, load state, ambient condition and recovery expectation. Include credible worst cases chosen by the system owner; do not create extra hazardous scenarios simply because the equipment can.<\/p>\n<p>The matrix also defines invalid runs. Examples include an input event outside its tolerance, a load state not reached, an instrument over-range, a trigger failure, or operation of a stop limit. Invalid data stay in the record but do not support the decision.<\/p>\n<\/article>\n<article class=\"stage\">\n<h3><span class=\"ez-toc-section\" id=\"Establish_a_stable_baseline\"><\/span>Establish a stable baseline<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Before an interruption is authorized, the lab confirms that the specimen and load are operating in the recorded state and that the load-terminal voltage is above Vmin with the intended margin. Baseline input, output voltage, load current or power, ambient and relevant temperatures belong in the record.<\/p>\n<p>If the baseline itself is unstable or below the acceptance window, stop. Hold-up analysis cannot repair an unsuitable steady-state design.<\/p>\n<\/article>\n<article class=\"stage\">\n<h3><span class=\"ez-toc-section\" id=\"Capture_synchronized_event_evidence\"><\/span>Capture synchronized event evidence<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>For each approved case, the laboratory records a time reference representing the defined input-interruption event and the voltage at the load boundary. It also records enough load information to prove that the intended load state was present. The qualified lab chooses the measurement architecture, ratings and acquisition settings.<\/p>\n<p>The raw trace remains evidence. Cropped screenshots without scale, channel identity, threshold, record length or instrument setup are not a complete acceptance record. Preserve the unaltered acquisition and a human-readable export tied to the specimen and test-row ID.<\/p>\n<\/article><\/div>\n<figure>\n            <img loading=\"lazy\" src=\"https:\/\/i1.wp.com\/www.wehopower.com\/wp-content\/uploads\/2026\/09\/weho-power-supply-hold-up-time-test-product-41c2d4572e40.png?quality=85&strip=all\" alt=\"How to Test Power-Supply Hold-Up Time Before Specifying a DC UPS  title=\" width=\"1440\" height=\"760\" loading=\"lazy\" decoding=\"async\" How to Test Power-Supply Hold-Up Time Before Specifying DC UPS title=\"\"><figcaption>Abstract decision timeline\u2014not a waveform, wiring diagram or measured result. The test record must supply the actual threshold, event, times and conditions.<\/figcaption><\/figure>\n<div class=\"protocol\">\n<article class=\"stage\">\n<h3><span class=\"ez-toc-section\" id=\"Reduce_each_valid_record_consistently\"><\/span>Reduce each valid record consistently<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Mark time zero at the approved input-interruption event. Mark the first load-terminal crossing below Vmin. Their difference is the measured hold-up interval for that record, <strong>t_measured<\/strong>. \u201cFirst crossing\u201d prevents a later rebound from hiding an earlier loss of validity.<\/p>\n<p>If the voltage never crosses Vmin inside the captured window, report it as greater than the valid observation window; do not invent an exact time. If noise near Vmin makes crossing ambiguous, apply the approved threshold\/hysteresis and uncertainty method or repeat with a corrected acquisition. Never smooth a trace after the fact merely to obtain a pass.<\/p>\n<\/article>\n<article class=\"stage\">\n<h3><span class=\"ez-toc-section\" id=\"Repeat_recover_and_sign\"><\/span>Repeat, recover and sign<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Repeat each case as required by the approved plan and retain the shortest valid t_measured. Confirm the separately approved recovery behavior after input returns: output restoration, load restart state, alarms and any unacceptable cycling. Recovery observations do not change the hold-up interval, but they can independently block acceptance.<\/p>\n<p>A result is usable only when a named technical owner signs the conditions, reductions, exceptions and decision. Procurement should receive the signed record, not a number copied into an email without context.<\/p>\n<\/article><\/div>\n<\/section>\n<section id=\"decision-rule\" data-step=\"05 \/ DECISION\">\n<h2><span class=\"ez-toc-section\" id=\"Apply_one_conservative_decision_rule\"><\/span>Apply one conservative decision rule<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Let <strong>t_required<\/strong> be the longest approved interruption the existing AC-DC supply is expected to bridge; <strong>m_measurement<\/strong> be the positive allowance approved for measurement uncertainty, repeatability and decision guard band; and <strong>t_measured,min<\/strong> be the shortest valid threshold-crossing interval among the covered records.<\/p>\n<div class=\"rule\">\n<p>The protocol issues <strong>PSU bridges<\/strong> only when:<\/p>\n<div class=\"formula\">t_measured,min \u2265 t_required + m_measurement<\/div>\n<p>Every other acceptance condition\u2014including the baseline, load state, input event and recovery checks\u2014must also pass. Otherwise, issue <strong>gap remains\u2014evaluate UPS<\/strong> or <strong>HOLD\u2014evidence incomplete<\/strong>, whichever describes the record.<\/p>\n<\/p><\/div>\n<div class=\"example\">\n<h3><span class=\"ez-toc-section\" id=\"Explicitly_hypothetical_threshold_example\"><\/span>Explicitly hypothetical threshold example<span class=\"ez-toc-section-end\"><\/span><\/h3>\n<p>Assume an approved 24 V load specification sets <strong>Vmin = 21.6 V<\/strong>. Assume the required interruption is <strong>20 ms<\/strong> and the laboratory&#8217;s approved measurement allowance is <strong>3 ms<\/strong>. The decision threshold is therefore <strong>23 ms<\/strong>.<\/p>\n<p>Now assume\u2014not measure, predict or attribute to any WEHO product\u2014that a completed laboratory record reports <strong>t_measured,min = 26 ms<\/strong> across the covered cases. The arithmetic margin over the 20 ms requirement is 6 ms, and 26 ms exceeds the 23 ms decision threshold. The record may state <strong>PSU bridges under the recorded conditions<\/strong>. It may not state \u201c26 ms hold-up for all units,\u201d \u201cUPS not needed in every installation,\u201d or \u201cthe product passed\u201d without the complete scope.<\/p>\n<p>This example contains no simulated waveform and no product-performance claim. Changing Vmin, load, input, temperature, sample or interruption definition invalidates the comparison until those conditions are tested.<\/p>\n<\/p><\/div>\n<\/section>\n<section id=\"published-product-rows\" data-step=\"06 \/ PRODUCT EVIDENCE\">\n<h2><span class=\"ez-toc-section\" id=\"Read_published_product_rows_as_leads_not_verdicts\"><\/span>Read published product rows as leads, not verdicts<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Three WEHO pages illustrate why a catalog value must be reopened as a controlled test question.<\/p>\n<div class=\"table-wrap\">\n<table>\n<thead>\n<tr>\n<th>Published page<\/th>\n<th>What the published page lists<\/th>\n<th>What remains unknown for this decision<\/th>\n<\/tr>\n<\/thead>\n<tbody>\n<tr>\n<td><a href=\"https:\/\/www.wehopower.com\/product\/rsp-200-ac-to-dc-power-supply-with-pfc\/\">RSP-200 AC to DC Power Supply with PFC<\/a><\/td>\n<td>A 200 W summary; 12 V, 24 V, 36 V and 48 V variants; 90\u2013264 VAC \/ 135\u2013370 VDC input; and a row labeled \u201csetup, rise, hold up time\u201d listing <strong>800 ms, 50 ms, 16 ms \/ 230 VAC (when fully loaded)<\/strong><\/td>\n<td>The page does not state the load-terminal Vmin used for 16 ms, tolerance, sample coverage or a customer interruption profile. It does not prove any user&#8217;s load will remain valid.<\/td>\n<\/tr>\n<tr>\n<td><a href=\"https:\/\/www.wehopower.com\/product\/rsp-500-ac-to-dc-power-supply-with-pfc\/\">RSP-500 AC to DC Power Supply with PFC<\/a><\/td>\n<td>A 500 W summary; 12 V, 24 V, 36 V and 48 V variants; 90\u2013264 VAC \/ 135\u2013370 VDC input; and the same labeled timing row listing <strong>800 ms, 50 ms, 16 ms \/ 230 VAC (when fully loaded)<\/strong><\/td>\n<td>Confirm the exact variant and current documentation. The public row does not provide the application Vmin, measurement tolerance, sample coverage or a customer-specific pass result. The family headline must not replace variant-level electrical review.<\/td>\n<\/tr>\n<tr>\n<td><a href=\"https:\/\/www.wehopower.com\/product\/psc-150-12v-24v-ac-to-dc-ups-3-years-warranty-switching-power-supply\/\">PSC-150 12 V \/ 24 V AC-DC UPS power supply<\/a><\/td>\n<td>PSC-150-12 and PSC-150-24; rated-current rows of <strong>7.5 A + 3 A (charge)<\/strong> and <strong>4 A + 1.5 A (charge)<\/strong> respectively; and a row labeled \u201cstart-up, rise, and hold time\u201d listing <strong>600 ms, 50 ms, 80 ms \/ 230 VAC<\/strong> and <strong>1200 ms, 50 ms, 16 ms \/ 115 VAC<\/strong><\/td>\n<td>The row does not state load, Vmin, ambient, tolerance or the exact measurement definition. Those times are not asserted here as battery-transfer time, seamless-transfer proof, battery runtime or customer-system performance. Battery compatibility and operating behavior require current model-specific evidence.<\/td>\n<\/tr>\n<\/tbody>\n<\/table><\/div>\n<p>These are statements about what each published page lists, not independent verification. The RSP timing rows provide a candidate condition\u2014230 VAC and fully loaded\u2014but still lack the load&#8217;s Vmin and the project&#8217;s event definition. The PSC page includes a hold-time row and battery-related functions, yet its published timing tuple cannot be relabeled as UPS transfer or backup duration.<\/p>\n<p>Use the product rows to choose questions for a controlled datasheet review and laboratory plan. Never average their values, apply one model&#8217;s condition to another, or claim that a larger wattage guarantees longer hold-up.<\/p>\n<\/section>\n<section id=\"ups-decision\" data-step=\"07 \/ NEXT GATE\">\n<h2><span class=\"ez-toc-section\" id=\"If_a_gap_remains_open_a_new_UPS_decision\"><\/span>If a gap remains, open a new UPS decision<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>When t_measured,min does not clear the threshold, first verify that the record is valid and that the requirement is real. If both stand, the existing supply has an evidenced ride-through gap for that scoped case. The next action is <strong>evaluate a DC UPS or another approved continuity architecture<\/strong>.<\/p>\n<p>That new work needs its own requirements: required service duration, source-transfer behavior, load peaks, simultaneous equipment and charge currents, battery voltage and chemistry, temperature, aging reserve, cutoff, alarm, recovery and safe shutdown. No battery Ah or runtime calculation belongs in this hold-up record.<\/p>\n<p>A UPS candidate must also be tested at the load boundary. A product label or nominal transfer claim cannot erase cable drop, control resets, source interaction or recovery behavior. For background terminology, the <a href=\"https:\/\/www.wehopower.com\/news\/switching-power-supply-efficiency-glossary\/\">WEHO switching-power-supply datasheet glossary<\/a> explains hold-up at a general level; this protocol supplies the narrower go\/no-go decision record.<\/p>\n<\/section>\n<section id=\"decision-record\" data-step=\"08 \/ HANDOFF\">\n<h2><span class=\"ez-toc-section\" id=\"Issue_a_decision_record_that_procurement_can_audit\"><\/span>Issue a decision record that procurement can audit<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>The final one-page summary should point to, rather than replace, the raw evidence.<\/p>\n<div class=\"records\">\n<div><b>1 \u00b7 Decision<\/b>PSU bridges \/ gap remains\u2014evaluate UPS \/ HOLD\u2014evidence incomplete.<\/div>\n<div><b>2 \u00b7 Scope<\/b>Model, variant, revision, samples, input, load, ambient, Vmin, interruption and margin.<\/div>\n<div><b>3 \u00b7 Result<\/b>t_required, m_measurement and t_measured,min, with test-row and raw-record references.<\/div>\n<div><b>4 \u00b7 Exceptions<\/b>Invalid runs, recovery issues, untested corners and document conflicts.<\/div>\n<div><b>5 \u00b7 Evidence<\/b>Approved plan, hazard authorization, instruments, raw captures, worksheet and signatures.<\/div>\n<div><b>6 \u00b7 Revalidation<\/b>Any design, load, cable, firmware, supply revision, input environment or requirement change.<\/div><\/div>\n<p>This format protects both engineering and sourcing. It makes a qualified \u201cbridges\u201d result usable without turning it into an unlimited catalog promise, and it makes a gap actionable without prematurely buying and sizing a battery system.<\/p>\n<\/section>\n<aside class=\"cta\">\n<h2><span class=\"ez-toc-section\" id=\"Prepare_the_evidence_before_requesting_a_model_review\"><\/span>Prepare the evidence before requesting a model review<span class=\"ez-toc-section-end\"><\/span><\/h2>\n<p>Send WEHO the exact supply model and revision, input condition, measured load profile, load-terminal Vmin and its source, ambient\/mounting condition, required interruption profile and the laboratory decision record. Request current controlled documentation and identify any remaining evidence before specifying a DC UPS.<\/p>\n<p>          <a class=\"button\" href=\"https:\/\/www.wehopower.com\/contact\/\">Contact WEHO with the scoped record<\/a><br \/>\n        <\/aside>\n<\/p><\/div>\n<p>      <\/main>\n  <\/div>\n<\/div>\n<p><script type=\"application\/ld+json\" class=\"weho-package-schema\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"BreadcrumbList\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/www.wehopower.com\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"News\",\"item\":\"https:\/\/www.wehopower.com\/news\/\"},{\"@type\":\"ListItem\",\"position\":3,\"name\":\"How to Test Power-Supply Hold-Up Time Before Specifying a DC UPS\",\"item\":\"https:\/\/www.wehopower.com\/news\/power-supply-hold-up-time-test\/\"}]}]}<\/script>\n<\/div>\n","protected":false},"excerpt":{"rendered":"<p>Define Vmin, run a controlled hold-up test, and compare measured ride-through with the required interruption before evaluating a DC UPS.<\/p>","protected":false},"author":1,"featured_media":17526,"parent":0,"menu_order":6,"comment_status":"closed","ping_status":"closed","template":"","format":"standard","meta":{"_acf_changed":false,"_joinchat":[],"footnotes":""},"news_category":[149,148],"class_list":["post-17530","news","type-news","status-publish","format-standard","has-post-thumbnail","hentry","news_category-blog","news_category-industry-news","entry"],"acf":[],"post_mailing_queue_ids":[],"_links":{"self":[{"href":"https:\/\/www.wehopower.com\/fa\/wp-json\/wp\/v2\/news\/17530","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.wehopower.com\/fa\/wp-json\/wp\/v2\/news"}],"about":[{"href":"https:\/\/www.wehopower.com\/fa\/wp-json\/wp\/v2\/types\/news"}],"author":[{"embeddable":true,"href":"https:\/\/www.wehopower.com\/fa\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.wehopower.com\/fa\/wp-json\/wp\/v2\/comments?post=17530"}],"version-history":[{"count":1,"href":"https:\/\/www.wehopower.com\/fa\/wp-json\/wp\/v2\/news\/17530\/revisions"}],"predecessor-version":[{"id":17533,"href":"https:\/\/www.wehopower.com\/fa\/wp-json\/wp\/v2\/news\/17530\/revisions\/17533"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.wehopower.com\/fa\/wp-json\/wp\/v2\/media\/17526"}],"wp:attachment":[{"href":"https:\/\/www.wehopower.com\/fa\/wp-json\/wp\/v2\/media?parent=17530"}],"wp:term":[{"taxonomy":"news_category","embeddable":true,"href":"https:\/\/www.wehopower.com\/fa\/wp-json\/wp\/v2\/news_category?post=17530"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}