Instruction manual

012-03175E
5
CAUTION: Whenever you open your
Electrometer, do not touch any of the compo-
nents on the printed circuit board other than the
battery holders or the trim potentiometers. The
printed circuit contains the high impedance
MOS-FET input which can be damaged just by
touching the wrong lead.
Battery Installation
To install or replace the batteries, remove the four
screws that fasten the front panel to the case, then
gently lift the front panel out of the case. Install the
batteries as shown in Figure 5. When removing and
installing the batteries, be careful not to bend the
battery clips or pull the battery wires out of the circuit
board. Place the new batteries in the clips with the
positive terminal closest to the printed circuit
board.Before replacing the front panel, test that the
batteries are good and the connections are secure by
flipping the FUNCTION switch first to B1 and then to
B2. The meter pointer should be deflected out beyond
the areas labeled B1 and B2, respectively, at the
bottom of the meter face. Replace the front panel.
PASCO’s Model ES-9065 Projection Meter can be
used with an overhead projector to display the Elec-
trometer readings for the whole class. The Projection
Meter connects directly to the OUTPUT jacks, red to
red and black to black.
To calibrate the Projection Meter:
① Set the FUNCTION switch to 3, and the Zero
Switch to ZERO LOCK.
② Turn the ZERO ADJUST knob until the meter on
the Electrometer reads as close to full scale as
possible (either postive or negative).
③ Adjust the CALIBRATE knob on the Projection
Meter so that the Projection Meter reads the same
as the Electrometer.
④ Turn the ZERO ADJUST knob until the Electrom-
eter and the Projection Meter read zero.
Checking Out Your Electrometer
① Follow the setup instructions on pages 2-3 of this
manual to check the batteries and zero the Elec-
trometer. If the batteries are low, see “Battery In-
stallation.” If the meter cannot be zeroed, see
“MOS-FET Replacement.”
② Calibration Test: Set the FUNCTION switch to
30 and connect the input to an accurate 30 VDC
source. If the meter does not read 30 volts ±5%,
see “Calibration.”
③ Input Impedance Test: Set the FUNCTION
switch to 30 and connect the input to a 30 VDC
source. Disconnect the input cable at the front
panel input connector. Record the meter reading
and the time. If the input impedance is sufficient, it
will take 15 minutes or longer for the meter reading
to decrease to 30% of its initial value. If the input
impedance is low, see “Repairs.”
④ Zero Drift Test: With the meter zeroed, short the
leads of the input cable together. Turn the Zero
Switch to PUSH TO ZERO and depress the knob,
then release it. The meter should read zero volts
and should drift by no more than 75 mV/minute.
At any time, depressing the Zero Switch should
bring the meter immediately back to zero. If the
zero drift is excessive, see “Repairs.”
IMPORTANT: A zero drift test is best
performed after the Electometer has been left
unused with the Zero Switch in the ZERO LOCK
position for at least four hours. During use with
high voltages, or during battery replacement or
other maintenance, charges may be produced on
the insulators of the input circuit. The bleeding
off of these charges may appear as excessive zero
drift.
Battery 1 (B1)
Battery 2 (B2)
Calibration
Potentiometer
Zero Calibration
Potentiometer
MOS-FET
Figure 5 Inside the Electrometer
Maintenance