Power supply ripple measurement is comparable only when the measurement conditions are comparable. Before judging a trace against a datasheet value, document bandwidth, the probe/reference arrangement, added termination components, output loading and the measurement location. A convincing screenshot with an undocumented setup is not an acceptance result.
Read the note that defines the number
The WEHO MDR-20 English product page lists 150mV peak-to-peak for the 24V model. Its ripple note specifies a 20MHz bandwidth, a 12-inch twisted pair and parallel 0.1µF and 47µF capacitors. The general measurement note identifies 230VAC input, rated load and 25°C ambient unless otherwise stated. Those conditions belong with the table entry; deleting them changes what the comparison means.
The authentic MDR-20-24 photographs and approved sheet agree on a 24V1.0A nominal output. The full-model identification is on the real right-side plate, not a large invented front label. A procurement record should retain both the actual unit identity and the document note used for the test comparison.
Separate three observations before diagnosing a supply
A source-output observation, a sensor-end observation and a probe setup’s own pickup do not answer the same question. A field measurement at a distant terminal includes the wiring and connected equipment context. It should not automatically be called the supply’s datasheet ripple measurement.
First decide whether the task is to reproduce the manufacturer’s specified method or to investigate the actual load’s voltage quality. Both may be useful, but they need separately identified locations and conditions. Record which observation is being discussed before assigning a cause or changing the product.
A useful measurement record
| Item to record | Question it answers |
|---|---|
| Full model/revision and source note | Which actual product and specified method are being compared? |
| Input, output load and ambient | Were conditions comparable to the adopted note? |
| Measurement location | Was the observation at the supply or at the equipment load? |
| Instrument bandwidth and channel setup | What observation range and signal handling were used? |
| Probe/reference connection and lead routing | What was the actual measurement loop and pickup context? |
| Termination network | Were the cited added components present and documented? |
| Trace scale, interval and repeat observations | Can the image be interpreted and reproduced? |
Have qualified personnel establish the safe instrument and reference arrangement. This guide does not direct connection of an ordinary grounded probe to mains or an unknown node, and it is not authorization to open an energized supply. Follow equipment and instrument instructions; a photograph of a control panel cannot establish a safe probing point.
Do not make two different methods look identical
If the local method does not reproduce the page’s bandwidth or network, retain the actual setup and state the difference. A value recorded under another method may be useful diagnostic evidence, but it should not silently be relabeled as a passing manufacturer-condition result.
Likewise, keep a peak-to-peak result distinct from a different statistical or frequency-domain quantity. Record the observation interval and state being measured rather than reducing a changing installation to a single context-free number. Avoid claiming that a capacitor added for a measurement proves the same behavior at every remote load in the machine.
The application photo should not invent a test result
The MDR-20-24 is 22.5mm across its narrow front,90mm high and 100mm from front to rear. Its drawing shows the rear DIN-rail arrangement. Circular front openings provide screw access; rectangular end-face openings are the conductor entries. Routing a wire into the front screw access or a blue ventilation slot would be a wrong installation, regardless of whether the model label looked correct.
The two scenes here depict protected dry control compartments and source-supported rear-rail relationships. They do not show live probing, a fabricated waveform, a calibration certificate or proof that a particular machine passed EMC. Exact controller and sensor compatibility must be confirmed from their own documentation.
What to ask when acceptance evidence is incomplete
Ask the supplier to confirm the full-model revision, maximum value and method note, applicable input/load conditions and any recommended interpretation of transient equipment states. Send the actual setup description with a trace rather than just the trace. If the source and measurement methods disagree, resolve that gap before concluding the supply is defective.
Frequently asked questions
Does 150mV peak-to-peak mean every oscilloscope view must show that or less?
The stated limit belongs with its documented conditions. An observation made elsewhere or with another setup cannot be treated as the same test without qualification.
Can an article image prove the supply passed the test?
No. These are application illustrations. A test claim needs an actual trace and reproducible condition record tied to the unit.
Does the approved PDF contain the complete probe note?
The adopted full sheet gives the model table and geometry; the detailed ripple-network note was obtained from the official English page. Both provenance paths are retained rather than pretending they are the same document.
Sources and revision boundary
WEHO MDR-20 English product page, reviewed 8 October 2026; exact approved enterprise-drive MDR-20/1.jpg,5.jpg and rear-mount source 3.jpg; complete MDR-20 electrical/mechanical specification. Physical input 100–240VAC0.55A is retained literally; the sheet’s wider input-range language is not a rewritten nameplate. No performed test, system certification or remote-load guarantee is asserted.
