WPI DAM50, Instruction Manual, Page: 9 / 16

DAM50
World Precision Instruments 5
AC or DC Recording?
It should be noted that DC recording with metal electrodes will invariably result in
excessively large galvanic potentials being applied to the amplifier’s input terminals.
This can result in overdriving the amplifier so that the POSITION control will not be
able to restore the operating baseline’s position. In this case, use Calomel or Ag-AgCl
electrodes, or use an external variable bucking potential; alternatively, resort to AC
recording.
MAINTENANCE
Testing the Amplifier
Instrument POWER is provided by two alkaline 9 volt batteries. Battery operation
results in lower internal noise level. Batteries can be tested by activating the BAT/CAL
switch. If a short tone is heard, the batteries are functional. Conversely if the tone is
absent, the batteries must be replaced. An additional function that the BAT/CAL switch
performs is to provide a low frequency square wave test signal which is applied to the
amplifier input. The amplitude of this signal is 100 microvolts when operating in either
of the two highest GAIN positions and 1 millivolt in the lowest GAIN position.
Mode Gain Cal signal Output
DC 10× 1 mV 10 mV
DC 100× 1 mV 100 mV
DC 1000× 100 µV 100 mV
AC 100× 1 mV 100 mV
AC 1000× 1 mV 1000 mV
AC 10,000× 100 µV 1000 mV