97029 Rev.C.2 09/2020

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7.0 Reference test points

Test points located in the battery compartment allow access to the control voltage used as part

of the motor feedback loop. Using an accurate AC DMM and/or an oscilloscope can help make

a determination as to the condition of the unit.

To access the reference test points, remove the battery cover (see section 4) and find the two

turret style connectors and connect the desired test leads. The “+” terminal is the AC output

voltage. The “-“ terminal is system ground.

CAUTION: When accessing the test points, proper precautions should be taken

against ESD (electrostatic discharge). Checking the test point voltage should be

done only in an ESD-safe environment.

7.1

Background information

The REF2500 contains an internal sine wave generator with a reference accelerometer in the

control loop to maintain a continuous output level of 1 g in either peak or RMS. The reference

accelerometer’s signal is fed through a charge amplifier to the control electronics.

Proper operation of the feedback control loop and accuracy of the internal voltage reference can

be verified by monitoring the voltage at the test point output. Since we are observing the

accelerometer signal, the test points will also provide information as to any mechanical or

significant electrical anomalies. In the event the REF2500 is dropped or otherwise abused,

measuring the output from the test points will confirm if the unit is still operational.

Figure 5: Test points

Test points