Fluke 825A - Page 27

825А
V102, 6BQ5
is
V104, OG3
V105, 12AX7
V106, 12AX7
V202, 5751 Eas
V203, 6AW8 modayn t
V204, OA2 E3
This chart is to be used under the following conditions:
Heater voltage 680 to No 680 to
6. 3 volts ас ЕЛІН 130 Сопп 730
Heater voltage
6.0 volts ас
Heater voltage
6.3 volts ас
(a) RANGE switch set to 500; (b) NULL switch
set to VT VM: (с) all voltage readout dials set to zero; (d) line voltage at 115/230 volts, 50 - 400 cycles;
and (е) all measurements made with а УТУМ from negative binding post to specified terminal.
Figure 4-6.
changes. For reasonable certainty of 0. 002% cell accu-
racy, the certified value should be known to six places.
Since the ESI voltage divider is accurate within +0. 005%,
the overall calibration system accuracy is between
0. 003% and 0. 007%.
b. PRELIMINARY CALIBRATION PROCEDURES
(1) Set 825A meter to zero with mechanical zero con-
trol.
(2) Set switches on 825A as follows:
RANGE 500
NULL VTVM
polarity + (positive)
all voltage read- 0 acy
out dials
(3) Place 825A and all calibration test equipment in
operation.
(4) Allow all equipment to warm up until it reaches
equilibrium temperature (about 1/2 hour).
(5) Set up the necessary equipment to provide DC
voltages of 500, 50, 5, and 0.5 V DC with an accuracy
of at least 0.01%. The recommended equipment and
method of connection is shown in figure 4-7.
(6) Set the proper standard cell voltage on the ESI
divider,
(7) Apply 500 volts DC into the divider from а 62
Model 301C or 301E power supply.
(8) Set ESI divider to 500 and zero galvanometer by
varying the output of the power supply while depressing
the coarse and then the coarse and fine push-button
switches. Voltages of 500, 50, 5, and 0.5 volts DC
(+0. 01%) are made available at the output posts by merely
TUBE VOLTAGE CHART
changing the position of the voltage selector switch on
the voltage divider.
c. NULL DETECTOR CALIBRATION
(1) Connect chassis ground to line ground.
(2) Short meter terminals and zero meter with ad-
justment screw on the front of meter case.
(3) Adjust УТУМ ZERO ADJ control R232 until 825A
meter indicates zero. If meter cannot be zeroed, clean
chopper as outlined in paragraph. 4-2c.
(4): Apply 500 volts DC to voltmeter.
(5) Adjust УТУМ GAIN ADJ control R222 for full
scale deflection.
d. 500 V DC REFERENCE SUPPLY CALIBRATION
(1) Measure reference supply voltage between pin-3
of V102 and negative binding posts.
(2) Center CALIBRATE control at its center of ro-
tation.
(3) Adjust 500 V REF ADJ control R121 until refer-
ence supply is 500. 0 (+0. 2 volts).
e. 500 V DC REFERENCE SUPPLY ADJUSTMENT
(1) Set switches on 825A as follows:
RANGE 500
NULL 0.1
Voltage read- 499. 910
out dials BIZ
(2) Apply 500 volts DC (+0. 01%) to voltmeter.
(3) Null 825A meter by adjusting CALIBRATE control.
(4) Advance OPERATE-CALIBRATE switch against
Spring tension to CALIBRATE and null meter by adjust-
ing REF-CAL ADJ control R318.
4-5