Instructions

AP033 Active Differential Probe

Troubleshooting

If the probe is not operating properly the problem may be the way in which it is used.

Before assuming the probe is defective, perform the following troubleshooting

procedures.

A. Trace Off Scale

This is typically caused by improper offset setting, or by an input signal that exceeds the

probe differential or common mode range.

1. Remove the input signal from the probe, return the offset to zero, and AutoZero the

probe. Does the trace return to approximately the center of the graticule? If not,

proceed to step 7.

2. Set the oscilloscope calibrator to output a 100-mV 1-kHz square wave. Using the flex

lead set, connect the probe

input to the calibrator output signal, leave the –input

open. Set the oscilloscope to 50 mV/div and 500 s/div. Is the displayed waveform a

100-mV 1-kHz square wave with the correct polarity?

3. Repeat step 2 with the – input connected to the calibrator and the + input left open.

In this case, the displayed waveform should be inverted.

4. Connect both the + input and – input to the calibrator output. Is the trace

approximately a flat line near zero volts?

5. If steps 1 to 4 give the correct results, the problem is likely a result of the input signal

exceeding the differential or common mode range.

6. Connect both the + input and – input to one of the two input signals. If the trace is

off scale, the input signal is probably exceeding the common mode range. Repeat

with the other input signal.

7. Is a ProBus Power Supply Overload error message displayed? If so, remove all other

ProBus accessories from the oscilloscope. Is the message still displayed? If so,

remove the AP033. Is the message still displayed? If so, the oscilloscope should be

returned for service.

8. If, after removing the AP033, the Power Supply Overload error message is not

displayed, the problem may be either the probe or the oscilloscope. Repeat the test

with a different ProBus accessory. If the message does not return with a different

accessory, the AP033 may be defective and should be returned for service.