Choose the meter question and reference
Select the appropriate virtual meter function and endpoints, predict the sign and meaning of a reading, and separate a load measurement from a path measurement.
The short version
- Write the question, function and two endpoints before reading the number.
- A voltage sign depends on the red and black lead order; it is not a motor-direction observation.
- Resistance requires a different circuit condition; it is not a substitute for a loaded voltage record.
Choose the question before the function
Our supplied drawing is a DC motor circuit. The question is how much voltage is across the motor during the recorded request.
Select virtual DC volts and the motor positive and negative terminals. Measuring either terminal against another reference answers a different question.
This is a simulated record exercise. It does not teach access to real terminals or establish that a real circuit is safe to test.
| Supplied record | Meaning |
|---|---|
| Question | Voltage across M1 |
| Function | Virtual DC volts |
| Red endpoint | M1+ |
| Black endpoint | M1- |
Function and input must agree
Fluke separates COM from its voltage/resistance input and its current input. Read the actual meter manual and its model-specific controls.
For this virtual voltage exercise, the displayed setup uses COM and V. An A-input selection does not become safe just because the dial says volts.
The simulator rejects a mismatched setup. That rejection is learning feedback, not a demonstration of real meter handling.
| Supplied record | Meaning |
|---|---|
| Virtual voltage setup | COM and V input |
| Function | DC volts |
| Current-input choice | Reject this voltage setup |
| Actual equipment | Use its complete instructions |
The black lead changes the question
The supplied run has B1+ at 12.40 V, M1+ at 11.90 V and M1- at 0.20 V, all relative to B1-.
Across M1+ and M1-, the result is 11.70 V. Between B1+ and M1+, the feed difference is 0.50 V.
Both readings can be correct. Their different endpoints make them different pieces of evidence.
| Red to black in supplied run | Meaning |
|---|---|
| M1+ to M1- | 11.70 V across load |
| B1+ to M1+ | 0.50 V across feed |
| M1- to B1- | 0.20 V across return |
A negative number is not a mechanical observation
Now leave red on M1+ but move the virtual black reference to B1+. The result becomes minus 0.50 V.
Red is half a volt below black in this supplied condition. That reading is not across the motor, so it cannot establish reverse motor operation.
Reversing a measurement pair changes its sign. A direction claim requires the appropriate circuit comparison and an actual recorded direction observation.
| Supplied record | Meaning |
|---|---|
| Red M1+ / black B1+ | -0.50 V |
| Red B1+ / black M1+ | +0.50 V |
| What changed | Lead order, not the motor |
| Motor pair | M1+ to M1- |
Do not mix voltage and resistance conditions
A resistance reading answers a different question from a loaded voltage reading. A powered circuit is not the condition for an ordinary resistance test.
The Fluke instructions require the relevant circuit power removed for resistance testing and address stored energy separately. They do not authorize an improvised isolation procedure.
No resistance or capacitor operation occurs in this activity. Choose supplied voltage records, or identify the missing qualified procedure when a task requires another measurement.
| Supplied record | Meaning |
|---|---|
| Voltage record | Named endpoints and operating state |
| Resistance request | Different safe test condition required |
| This activity | Virtual voltage records only |
| Missing procedure | Ask qualified lead |
Predict the discriminating comparison
Suppose a note says low voltage at the motor but omits its black reference. What can that phrase establish?
Very little. It may describe the load voltage, a feed drop or a terminal-to-frame reading. Ask for the pair and operating state.
Then predict how each possible reading would change your next decision. Do not collect numbers just to fill a checklist.
| Supplied record | Meaning |
|---|---|
| Missing black endpoint | Meaning unresolved |
| Across load | What the load sees |
| Across feed | Loss over that section |
| Across return | Loss over return section |
Apply the setup to an unfamiliar circuit
The related feed activity uses its own named nodes and supplied fault. Keep the same discipline even when the drawing layout changes.
Choose mode and both endpoints before collecting evidence. Keep readings with their conditions when you interpret the loss.
In the case, a minus sign prompted an unsupported motor-direction claim. Correct that claim without declaring the motor fully healthy.
Keep the meaning with the number
Record function, inputs, red endpoint, black endpoint, units and operating condition. A bare number is not a diagnostic conclusion.
Use the supplied circuit to predict the sign and distinguish a section measurement from a load measurement.
The exercise demonstrates record interpretation only. Real measurement technique and safety require the appropriate equipment procedure and qualified observation.
Shop tip
Josh: Complete the sentence: this number is volts between these two points, during this condition.
Where this comes from
- Fluke 110/113/114/115/117 Users Manual; March 2020; printed 2,4,7-9 (PDF 6,8,11-13), functions, terminals, resistance, voltage and current warnings; checked 2026-11-04. Scope: Distinguish the meter function, input and measurement pair. No live-equipment access, isolation or capacitor procedure is taught. https://media.fluke.com/5e1db354-3a6e-49cf-9edd-b10800c0e608_original%20file.pdf
- Original Rigprobe teaching examples, 2026-11-04. Identifiers, diagrams, connector layouts, timings and readings are invented problem data, not OEM drawings, specifications or universal acceptance limits.
Try it on a service call
Put the lesson to work on a hands-on troubleshooting case.