Macro 12 provides terminal run/direction commands with an analogue speed reference on supported control units. The input hardware setting, p0756 signal type and scaling endpoints must agree; selecting the macro alone does not calibrate the signal.
Separate the run command from the speed reference
In the referenced CU240E-2 arrangement, DI0 handles ON/OFF1, DI1 handles reversing, DI2 acknowledges a fault and AI0 supplies the speed reference. A changing analogue signal is therefore not a start command. A zero reference is also not a safety stop.
Use a clear signal list before commissioning: controller output range, drive input channel, expected engineering range and response to a broken signal. Include the actual control-unit order number and firmware. This prevents a technician from applying a familiar 0–10 V configuration to a 4–20 mA loop.
For a unidirectional application, define how negative references and reversing commands are handled. Do not leave the physical direction selector unexplained merely because the process normally runs forward.
Match the electrical input and parameter type
On the referenced CU240B/E-2 family, the analogue-input voltage/current switch and p0756 must match. Set the electrical mode with power isolated as specified by the manual. Select the signal type before editing the scaling: changing p0756 can reset the endpoint values.
| Item | Meaning | Commissioning check |
|---|---|---|
| p0756 | Analogue input type | Match the supported voltage/current range |
| p0757 / p0758 | First input / percentage point | Define the low endpoint |
| p0759 / p0760 | Second input / percentage point | Define the high endpoint |
| r0752 / r0755 | Measured input / scaled input | Compare electrical and scaled values |
| p2000 | Reference speed/frequency | Confirm what 100% represents in the project |
Use the channel index belonging to the wired input. Do not apply a voltage source to a current-configured input or assume that all analogue grounds can be joined without consulting the installation drawing.
Worked 0–10 V and 4–20 mA examples
The examples below assume 0–100% corresponds to a 0–50 Hz reference, with no additional setpoint contribution or limiting. They illustrate the arithmetic; they are not universal commissioning values.
Percentage = Y1 + (Input - X1) × (Y2 - Y1) / (X2 - X1)
Example frequency request = Percentage / 100 × 50 Hz| Input range | Low point | Midpoint | High point |
|---|---|---|---|
| 0–10 V | 0 V → 0% → 0 Hz | 5 V → 50% → 25 Hz | 10 V → 100% → 50 Hz |
| 4–20 mA | 4 mA → 0% → 0 Hz | 12 mA → 50% → 25 Hz | 20 mA → 100% → 50 Hz |
For 4–20 mA, subtract the 4 mA live zero before dividing by the 16 mA span. Dividing 12 by 20 would incorrectly give 60%. Keep the calculation in floating-point arithmetic when implementing a comparison in the PLC.
If the process calls for a nonzero minimum operating speed, document whether that is created by the analogue characteristic, a drive limit or the PLC reference. Applying it in two places can produce a misleading calibration result.
Practical lab: verify the whole signal chain
- Back up the project and record the present command source. Confirm that the selected commissioning macro is available for the installed drive.
- Use a suitable signal source and approved wiring. Start with motion inhibited; confirm the actual electrical value at the correct input.
- Apply the low, middle and high test points. Record measured input, scaled percentage and expected speed request at each point.
- If the raw value is right but the percentage is wrong, inspect type, channel index and endpoints. If the percentage is right but the request is wrong, inspect reference scaling and the setpoint path.
- Run a controlled motion test only after the static checks pass. Observe actual speed after the configured ramp has settled.
- Test signal loss using the approved procedure. Record the diagnostic, resulting drive behavior and recovery sequence.
- Save to nonvolatile memory, upload the verified configuration and record the calibration equipment used.
A useful acceptance sheet includes both the rising and falling sequence of test points. This makes it easier to distinguish a fluctuating source, mechanical response and a systematic scaling error.
Find scaling and signal-loss faults
| Observed behavior | Likely area to investigate |
|---|---|
| Zero or saturated raw input | Wiring, common, voltage/current selection, source range |
| Raw input correct; percentage wrong | p0756, selected channel and scaling endpoints |
| Percentage correct; requested speed wrong | Reference quantity, limits or additional setpoint |
| Request correct; motor response differs | Ramp, control mode, load or drive state |
| Broken loop appears as a valid low demand | Signal-loss configuration and application response |
Noise should be investigated before adding heavy filtering. Check cable routing, shielding and reference connections against the installation guidance. Excessive filtering can delay a real process change and make a responsive controller appear unstable.
Keep run permission and signal quality as separate observations. A plausible number on an HMI is not sufficient evidence that the drive is receiving a healthy control reference. See G120 wiring and terminal parameters for the companion terminal guide.
Frequently asked questions
Does macro 12 automatically configure 4–20 mA?
No. Check the hardware input mode, supported signal type, selected channel and scaling endpoints. Verify the low, middle and high points with a suitable signal source.
Why does 5 V not give 25 Hz?
That result assumes 0–10 V maps to 0–100% and 100% represents 50 Hz, with no other setpoint contribution or limit. Inspect the complete signal path.
Is removing the analogue reference an emergency stop?
No. Use the machine’s designed and validated safety function. Reference loss must also have a documented operational response.
Technical references
Use the document edition matching your installed hardware and firmware. The linked manuals establish the device-specific facts; the worked examples and check sheets are training exercises.