Test Function - Tektronix DC 5010 Anleitung

Operating Instructions-DC 50 10
Probe Compensation
The DC 5010 has been specifically designed to be com-
patible with standard probes when in 1 MQ termination;
however, the operator must still be sure that the probe is
properly compensated.
In the DC 5010, a probe compensation (PROBE COMP)
function is built into the counter. It allows the user to com-
pensate the probe in place and without the use of an exter-
nal oscilloscope.
A square-wave signal of approximately 1 kHz and an am-
plitude of approximately 5 V is provided at the front panel
PROBE COMP tip jack.
Connect the probe tip to the PROBE COMP tip jack be-
fore entering the PROBE COMP mode.
The counter should display a zero for the most significant
digit (far left) and a zero for the least significant digit (far
right). The far left digit is for a probe connected to CHAN-
NEL A and the far right digit for a probe connected to
CHANNEL B. No decimal points or annunciators should be
illuminated.
With the probe connected and the square-wave signal
applied, perform the following steps.
1. Slowly rotate the probe adjustment in either direction
until the display changes to a continuous 1 reading for the
channel being compensated.
2. Slowly reverse the rotation of the probe adjustment
until the display just goes back to a
0.
At this point, the
probe will be compensated. A 1 indicates that the probe is
over compensated; a 0 indicates under compensation. Final
adjustment should be made in the direction where the 1 just
changes to a 0.
N O T E
If a display goes to a I and remains in that condition
for one or more complete revolutions of the probe ad-
justment, press the R E S E T pushbutton to clear the
condition. This can occur if the connection to the
square-wave source became open during the adjust-
ment procedure.
Test Function
A 000 display in the three MSD's for the TEST function is
an indication that the microprocessor has checked itself.
The test also checks the internal serial data path, the integ-
rity of the internal counter chain (accumulators), and, as a
by-product, the operation of the digital-to-anallog converter
(trigger levels) and input amplifier circuits.
The random-access memory space (RAM) is not checked
during this front panel self-test; the RAM is checked only at
power-up.
N O T E
If the C H A N N E L
A
or C H A N N E L
B
input,; are con-
nected, the peaks of the input signals must be within
the triggering level range of the counter fcr the test
function to operate properly. If a failure occurs, first
disconnect any C H A N N E L
A
or C H A N N E L . B inputs
and repeat the test. A connection to the arming input
may also cause improper operation.
The gate light will flash once each time a full test cycle
has been completed. If a failure is ever noted, the error code
of that failure will be displayed in the three extreme left digits
of the seven-segment display and the cycling will halt. The
DC 5010 will stay in test mode until another function is
selected.
Arming (ARM Input)
Arming provides a means by which single events or sets
of events can be selected for measurement within a com-
plex analog or digital signal. Figure 2-9 shows three different
examples of arming.
The ARM input requires TTL signal levels. With no signal
attached the ARM input is normally pulled high and is thus
continuously armed. When the ARM input is pulled low, the
counter is prevented from starting a measurement. Arming
may be used in all measurement functions with the excep-
tion of TIME MANUAL, PROBE COMP, and TEST. In these
three functions the ARM signal must be high.
When the arming signal changes to a high state, the first
subsequent Channel A event will start the rrieasurement
process. When the arming signal changes to a low state, the
next Channel A event will stop the measurement process.
Therefore, the counter can be controlled as to wlhen, in time,
a measurement will be made (even in complex waveforms).