Comparing Power Supply Ripple: Ask for the Measurement Conditions

A smaller number is not a complete comparison

When two power supply quotations list different ripple figures, purchasing needs more than the smaller number to make a decision. First establish what each supplier measured, under which conditions, and whether the result applies to the configuration being quoted.

Ask your equipment engineer to define the requirement before requesting a special low-ripple option. Keep the required limit, the supplier's specification and a sample measurement in separate fields. A result from one sample should not silently become the guaranteed limit for every delivered unit.

This guide is a procurement checklist for reviewing evidence. It does not set a universal ripple limit or claim a measured result for a Voltivo Power model.

Why the measurement method belongs in the discussion

Tektronix explains how probing affects power supply voltage measurements. Probe attenuation and the instrument noise floor can affect the ability to observe small signals. Long ground leads can introduce ringing and pick up noise. Coupling choices also matter: AC coupling removes the DC component but can hide low-frequency drift.

For purchasing, the practical implication is to request the method alongside the value. An unexplained difference between two reports may need a technical review of the setups before it supports a supplier ranking. Have a qualified engineer select the measurement arrangement, including an appropriate ground-referenced or differential approach; this checklist is not a bench-testing procedure.

Use one comparison sheet for every supplier

Send the same blank fields with each RFQ. Ask suppliers to identify unavailable information explicitly instead of filling gaps with assumptions.

Value and status

State the units, whether the value is peak-to-peak or RMS, and whether it is a specified maximum, typical value or individual sample result.

Product identity

Record the exact model, output configuration, cable or connector option, sample identifier and document revision.

Operating conditions

Request the input condition, output load, operating mode and temperature associated with the quoted figure.

Measurement arrangement

Ask for the test point, instrument and probe, bandwidth setting, coupling, acquisition settings and any specified external components.

Supporting record

Request the relevant datasheet section or test report reference, with a labeled waveform where available.

Leave numerical acceptance limits and required test settings to the responsible technical reviewer. Do not insert a familiar bandwidth or a catalog value from another model as a default requirement.

Resolve differences before choosing a quotation

Consider an illustrative comparison: one supplier offers a typical figure, while another specifies a maximum under stated conditions. Treat those as different evidence types. Ask whether the first supplier can commit to the required maximum and whether both proposals cover your intended configuration.

Likewise, if one report omits the measurement location or load, mark the comparison as incomplete. A useful clarification request is: “Please identify the conditions for this value and confirm which requirement in our brief it addresses.” Record the response next to the original figure rather than replacing the original wording.

If engineering concludes that the two methods are not comparable, ask for aligned evidence or an agreed sample evaluation. Keep any extra evaluation cost and lead time visible in the commercial comparison.

Carry the agreed requirement into the order

Before releasing an order, link the accepted limit and method to the configuration revision. Identify who accepted the evidence and list remaining exceptions. If a report covers only a particular operating condition, do not expand that acceptance to other conditions without review.

For a Voltivo Power inquiry, include the required output, application, quantity, destination markets and any equipment-level ripple requirement. Attach or reference your engineering brief and flag the evidence needed before sample approval. Model-specific performance, available reports and evaluation arrangements must be confirmed during the quotation process.