Dccurrentmeasutement; Accurrentmeasurement - Keithley 177 Instruction Manual

A. Select 200 range.
D. Adjust front panel ZERO knob for a display indication of
B. Disconnect the test leads at the circuit to be measured
O.OOO,rA * ,001 flashing.
and short them. If measurement is to be made right at
2. After adjusting ZERO, use the Model 177 to measure DC
the INPUT terminals (no test leads used) place a short, current as follows:
such as a piece of copper wire, across the binding
posts.
CAUTIONS
C. Adjust the front panel ZERO knob for a display indica-
Do not install e larger capacity fuse then
tion of 0.000 *O.OOlG (flashing). The nominal ZERO
the one originally supplied L?Al. Current
adjustment span is 200mD.
fuse FlOl (shown in Figure 5-4) protects the
instrument against over-current.
NOTE
The specified accuracy for the 2OD and 2OOG
A. Select the desired range from the six ranges available.
ranges assumes that ZERO was adiusted on the
8. Connect the circuit to be measured to the INPUT ter-
20irange. Re-adjust zero on the 2dg range each
time that a different set of leads is used or
whenever measurements have been made on
minals.
C. Read the displayed polarity, digits and decimal point.
Select the next higher range if overrange is indicated.
either the two lowest DC voltage ranges or any
DC current range. The zero setting for those
measurements will be different than the zero set-
ting of ohms, Also, re-adjust zero whenever the
instrument is used outside the temperature
range of 18O to 28OC.
D. Reconnect the test leads to the circuit to be measured.
E. Select either 2OD range or 2000 range. Read the
displayed digits and decimal point.
NOTE
An input overload to the Model 177 may cause a
temporary zero shift due to thermal gradients.
2.12 DC CURRENT MEASUREMENT
2.13 AC CURRENT MEASUREMENT
The Model 177 measures AC current from 1OnAldigit to 2A.
over five ranges. (The' 20r~A and 20M ranges are not
operative. See note below.1 The 200r~A range is direct-
reading in microamperes. The remaining AC current ranges
are direct-reading in milliamperes. The maximum reading is
19999. Overrange is indicated by a flashing 0000. Overload is
protected by fuse FlOl, a 2A, 3AG normal-blow fuse. The
instrument measures the true root mean square ITRMSj of
waveforms in the frequency range of 45 to 10kHz. Use the
Model 177 to measure AC current as follows:
1. Turn on power and set the AC/DC pushbunons to in or
AC position. Depress the A pushbunon.
CAUTION
The Model 177 measures DC current from lnA/digit to 2A.
over six ranges (the 20M range is not operative and the
Do not install a larger capacity fuse then
instrument will read zero if 20M pushbutton is depressed).
the one supplied. Current fuse FlM (shown
The maximum reading is 19999. Overrange is indicated by a
in Figure 5-41 protects the instrument
flashing 0000. Overload is protected by fuse FlOl, a 2A 3AG
against over current.
normal-blow fuse. Nominal settling time for DC current
2. Connect the circuit to be measured to the INPUT terminals
ranges is one second to within one digit of final reading ex-
and select the desired range from the five ranges available.
cept three seconds on 20pA range.,
NOTE
1. Before making DC current measurements, the front panel
ZERO must be adjusted on the 20@ range. This adjust-
The 20/1A and 20M ranges are not operative for
AC current measurements. If the 20uA push-
ment is necessary to remove any offset that was intr-
button is inadvertently depressed, an overrange
oduced by adjusting ZERO for a low DC voltage measure-
mentor a low g measurement. This adjustment will also be
will be indicated, signalling the user to go to the
necessary whenever the instrument is used outside of the
next higher range. If the 20M pushbutton is de-
temperature range of 18O to 28Y. The specified accuracy
pressed, the instrument will read zero.
for the DC current ranges assumes that ZERO was ad-
3. Read the displayed digits and decimal point.
justed on the 2OpA range. Adjust ZERO as follows:
A. Disconnect all circuits from the Model 177 INPUT ter-
NOTE
minals. The INPUT terminals must have an open cir-
AC accuracy is specified for 2000 counts and
cuit~ above. The method of calibratina the converter
_-...
8. Turn on power and set the AC/DC pushbunon to the
out or DC position.
C. Depress A and 20~ pushbuttons.
may yield an offset up to 80 digits with the
Model 177 input shorted. This does not affect in-
strument accuracy. There will be some addi-
tional measurement error for signals with a crest
2-7