Control Summary
about connecti
ng a probe is available. (See page 8, Connecting a C urrent Probe
to the Amplifier.)
OUTPUT Connector
The amplifier current measurement output is acces sed at the OUTPUT connector,
which s hould be connected to the oscilloscope input. Attach one end of a 50 Ω
BNC cable to this connector and the other end to a 50 Ω vertical input of your
oscilloscope. The output impedance of the amplifier is 50 Ω.
To get a direct readout of current on your Tektronix oscilloscope, use the
TEKPROBE interface cable to connect the amplifier to your oscilloscope.
NOTE. To obtain accurate measurements, the input impedance of your
oscilloscope must be 50 Ω. Make sure your amplifier OUTPUT is connected to an
oscilloscope input using a 50 Ω BNC cable, and that the oscilloscope i nput is set
to 50 Ω impedance. The proper cabling is shown. (See Figure 1 on page 1.)
If your oscilloscope does not have 50 Ω impedance settings for inputs, you can
place a 50 Ω feedthrough termination on the oscilloscope input and connect
the amplifier output cable to the termination. Do not place the feedthrough
termination a t the amplifier end of the BNC connecting cable.
Probe DC Gain Adjust
(located on probes)
After the PROBE DEGAUSS AUTOBALANCE routine has been run, the probe
and amplifier system will meet all published specifications. However, if you want
to improve the tolerance of the system accuracy, or to intentionally offset the
accuracy to make up for total system errors, you can manually adjust the gain of
the probe. See the service manual for adjustment procedures and locations.
NOTE. You should be careful to note the existing position of the DC Gain
Adjustment before you alter it, so that you may return it to the initial, calibrated
position. By altering the DC Gain Adjustment, you may cause the probe to not
meet the warranted DC Accuracy specification.
For example, the typical accuracy of the TCP312 probe on the 1 A/V range is
1%. Ifyouwanttomeasurea3Ap-p,1kHzsquarewaveandneedincreased
accuracy (better than 0.25% is attainable), first adjust the TCP312 on the 1 A/V
range setting using a calibrated 3 Ap-p, 1 kHz square wave source. Then, attach
the probe to your circuit and take your measurement. Remember, altering the DC
Gain Adjustment may cause the probe to not meet the warranted DC Accuracy
specification.
GPIB Operation
The TCPA300 and TCPA400 Current Probe Amplifiers do not have direct GPIB
connections. However, you can use a computer to control the oscilloscope that the
amplifier is connected to, enabling you to change the time and scale factors of
your current measurements over the oscilloscope GPIB bus.
TCPA300/400 Amplifiers and TCP300/400 Series Current Probes User Manual 19
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