DATA PRECISION 938 User Manual

42-5124
MODEL 938
1.2 OPERATING FEATURES
Model 938 input circuitry is protected by a 1/4-amp Fast-Bio
fuse against input overloads. The liquid crystal display
assembly is built around large (0.5") digits, and is easily read
under a wide range of ambient lighting conditions, indoors or
out. The decimal point is automatically positioned in the display
by the action of selecting the range scale, so that the results
may be read directly in the units established by the range scale
selected. The full scale range values are printed adjacent to the
range-scale -select pushbuttons, and include the capacitance
units, as well as the values.
Out-of-range values are indicated by blanking all but the MSD
and decimal point. This prevents erroneous readings,
while at the same time providing an indication of an
operable meter. The meter also contains a sense and display cir 
cuit to Indicate when the battery (or ac source power) is low. Ap 
pearance of the LO BAT display indicates that the battery is
below 7 volts, or that the ac source is at a lower voltage than
specified.
One internal trimmer is used to calibrate the meter for accuracy
on all ranges. One external thumbwheel adjusts the zero and
simplifies the meter use from one application to another where
different levels of stray capacitance to affect the measurement
results.
1-2
MODEL 938
SPECIFICATIONS
Chapter 2
SPECIFICATIONS
2.1 CAPACITANCE MEASUREMENT
NOMINAL
RANGE
MAX IN-RANGE
DISPLAY
RESOLUTION
200 pF
199.9 pF
0.1 pF
2 nF
1.999 nF
1 pF
20 nF
19.99 nF 10 pF
200 nF
199.9 nF
100 pF
2 m F
1.999 m F
1000 pF
20 m F
19.99 m F
0.01 m F
200 m F
199.9 m F
0.1 m F
2000 m F
1999 m F
1 m F
Accuracy (1 yr., 23°C ± 5°C):
±(0.1% Reading + 1 digit + 0.5pF)
Except ±(1.0% reading + 1 digit) on 2000 m F range).
Temperature Coefficient:
±(0.01% input + 0.01 %range)/°C
Except ±(0.02% input + 0.02% range)/°C on 200 pF and
2000 m F range.
Excitation Voltage:
2.8 volts peak, maximum
High input terminal is always more positive than low ter 
minal
Measurement Technique:
Dual-slope integrating A/D converter; measures ratio of
change in charge to change in voltage (Capacitance).
Overload:
Input protected by 1/4 amp 250V fuse
Controls:
Eight range push buttons, On/Off, and zero adjust.
2-1

DATA PRECISION 938 Specifications

General

Brand	DATA PRECISION
Model	938
Category	Measuring Instruments
Language	English