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Top of Board
Bottom of Board
Dec Com
1
A 10° DEC/Enable
Busy/Done
2
B 10¹ DEC/Enable
Hold
3
C 10² DEC/Enable
Polarity
4
D 10³ DEC/Enable
SIGNAL LO
5
E
BCD 1
BCD 4
6
F
BCD 8
BCD 2
7
H SIGNAL HI
Display Enable 8
J
Digit 5 Enable
+5 VDC Power 9
K Power Ground
N/C
10
L
Power Ground
Figure 3. Connector Pin Wiring
HOLD FUNCTION:
Pin 3 is a control input for the
reading hold function which can be controlled from
either a logic level (0V or +5V) or a contact-closure.
A low logic state or contact-closure to ground will
cause the meter to cease making measurements
and hold the reading of the measurement on
progress. A high logic level or open contacts will
cause
the
meter
to
resume
measurements.
DISPLAY DIMMING AND BLANKING:
display and polarity enable functions are used for
dimming and blanking the display by controlling the
supply voltage to the readouts. Connecting pin 8,
the display enable function, to pin 9, the +5VDC
supply, illuminates the numerals at full brightness.
Polarity enable is provided separately so that
polarity sign can be blanked (remove R2) for
measurements having no polarity. The entire
readout can be dimmed to any convenient
brightness by connecting a resistor or rheostat
between the +5VDC power (pin 9) and the enable
line (pins 8).
BINARY
CODED
DECIMAL
OUTPUTS:
The 1, 2, 4, and 8 multiplexed BDC
outputs are available on connector pins E, 7, 6 and
F, respectively. When digit 5 enable (pin J) goes to
a "low" logic level (zero), the 1, 2, 4 and 8 BCD
outputs represent digit 5, the most significant digit.
When digit 4 enable (pin D) goes "low", the BCD
outputs represent digit 4 and so on, to the least
significant digit. For connector pin information refer
to Figure 3. Digits are scanned from most significant
to least significant digit. Each digit goes "low" for
approximately 1-2/3 milliseconds, and there is no
gap between successive digit enables except when
the meter goes into overload. For the BCD outputs,
.
"high" = true = +5VDC
BUSY
: (pin 2) When the meter is in the process of
making a measurement, the "busy" output is "high"
(+5VDC). When the measurement is completed, the
"busy" output goes "low" (0V).
POLARITY OUTPUT:
When the polarity of the
input signal is positive, pin 4 goes "High" (+5V).
When the polarity of the input signal is negative, pin
4 goes "Low". This output becomes valid at
integrate and remains correct until it is re-validated
for the next measurement. It is valid when the
"busy" output is low.
RANGE MODIFICATION
The range of the meter can be changed as follows:
1. Insert the blade of a small screwdriver between
case and rear cover, midway on case above
printed circuit connector, and pry gently outward.
Remove rear cover.
2. Slide meter assembly form case. Observe that
read filter is a loose piece and will be required for
reassembly.
3. Observe resistor values for R4 and R6 and
compare to Table I and Figure 4. Install resistors
of values specified in Table I to obtain desired
range.
4. If a decimal point is desired, refer to instruction 7
under "Operation".
5. Clean all solder joints and adjacent areas on
printed circuit board to minimize leakage paths.
6. Reassemble meter.
7. A range modification resistor set for
PM-452 is available from your distributor, specify
NLS part number 39-356.
TABLE I: RANGE RESISTOR VALUES
Range
2 V
20 V
repetitive
200 V
1000 V
The
(BCD)
Figure 4. Component Location
CALIBRATION
To calibrate the instrument, perform the following
steps:
1. Allow the meter to warm up for at least
five minutes.
2. Set the power supply voltage to +5V ±2%.
3. Apply DC input signal voltages as follows:
RANGE OF
INSTRUMENT
2 V
20 V
200 V
1000 V
4. Adjust potentiometer at rear of meter until display
agrees with input.
5. Disconnect calibration voltage and power supply
input.
R4
R6
JUMPER
OMIT
909 KΩ 1%
100 KΩ 1%
10 MΩ 1%
100 KΩ 1%
10 MΩ 1%
10 KΩ 1%
CALIBRATION
VOLTAGE
+1.9990 V
+19.990 V
+199.90 V
999.0 V
CURRENT MEASUREMENT
DC current measurements can be made using an
externally mounted shunt resistor. Use meter in the
2 Volt range and connect shunt resistor between
pins 5 and H of the edge connector.
If the current being measured enters pin 5 and exits
from pin H, the polarity displayed will be positive.
The value of the shunt resistor should be chosen as
set forth in table II. Note that at full scale, the voltage
drop across the shunt resistor is 1.9999 Volts. The
measuring circuit should be carefully examined to
insure that this voltage drop does not introduce
excessive error into the measurement.
WARNING: This meter is frequently used
on the high side of the current source to be
measured. This arrangement may cause a
short between the circuit high side and
ground with possible damage to the meter
and circuit. To prevent such a short, an
isolated
meter
power
recommended.
TABLE II: SHUNT RESISTOR VALUES for
Current Measurement
FULL SCALE
CURRENT
20 µA
200 µA
2 mA
20 mA
200 mA
2 A
MAINTENANCE
Due to the solid-state construction and 100%
test and calibration of your PM-452 is an
extremely reliable instrument. However in the
event of trouble, the LED readouts and the
major integrated circuit are plug-in. They can
be easily replaced without soldering.
Specifications Subject to Change without Notice
NON-LINEAR SYSTEMS
Originator of the Digital Voltmeter
San Diego, CA
Phone: (619) 521-2161
Fax: (619) 521-2169
Email:
sales@nonlinearsystems.com
supply
is
SHUNT
RESISTOR
100 KΩ
10 KΩ
1 KΩ
100 Ω
10 Ω
1 Ω
11-15
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