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Test points
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.
Figure 5: Test points
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 1g 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.
