54
7. Connect an oscilloscope to J2 pin-E with respect to J2 pin-B to see the 1µs, TTL, interrogation pulse
(see Figure D-4). Transducers with stroke lengths ≤ 12 inches should have a negative signal and trans-
ducers with stroke lengths 13 inches or longer will have a positive signal.
8. Disconnect power and connect transducer back to the DIB and look for the same voltage and signal
levels as in step 6 and 7 with the power restored.
9. Connect the oscilloscope to J2 pin-C with respect to J2 pin-B to see the transient return pulse along
with the recirculations (see Figure D-5). If these signals are not present, go to the next step.
10. Disconnect power and isolate J2 pin-C (return pulse) from the DIB. Connect the oscilloscope to pin-C
on the transducer side and restore the power. The signals should look like Figure D-5. If not, send the
transducer to MTS Sensors for repair.
D.5 Counter Card Digital Output Test Procedure
The Counter Card output, (14-18 bits typical), is a true high TTL level signal nominal 0 to 5 volts DC.
The receiver device must be selected to interface with the TTL level signal of the Counter Card. Most
devices offer a TTL input option or a specific model selection designed for TTL only. If the user suspects
an improperly selected or malfunctioning receiver device, the Counter Card output may be tested using
LEDs.
Perform the following procedure:
1. Disconnect the receiver device from the binary output of the Counter Card. This is usually performed at
the receiver device input terminals.
2. Connect 4 or more LEDs (rated for 3-5 Vdc, 50 mA maximum) between the binary output and power
supply ground as shown in Figure 9-1. Select the bits (or digit) which will give a reading which is easi-
ly interpreted. (Four of the “middle” bits for natural binary; tenths or units place for BCD). The LEDs
light when the bit is high. (Note that output voltage will drop under load - refer to a TTL data book
for details.)
3. With the above test set-up procedure, some of the LEDs should light immediately. If no LEDs light,
move the magnet through the stroke of the transducer and ensure that one or more LEDs light. If
none respond, recheck the wiring of the LEDs and the power supply connections to the Digital
Counter Card (Pins 1 and 2).
Figure D-2
Testing Counter Card Output
4. To check the Counter Card reading, move the magnet between two measured positions on the stroke,
and record the LED readings, as “HI” or “LO”. Take the complement of the readings, and calculate the
decimal equivalent of the readings. Refer to Table 1D (next page).
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