Test Pulse Width; Test Pulse Frequency; Test Stimulus Duration - Somatics THYMATRON System IV Service Manual

3.4

TEST PULSE WIDTH

Change horizontal deflection to 100 µsec/div and push TREAT button. Observe wave
shape such as in fig. 3.5. The pulse width should be 0.5 msec ±5% from the start of the
rising edge to the start of the falling edge of the pulse.
3.5

TEST PULSE FREQUENCY

Connect a frequency counter to the dummy load divider as in fig. 3.2. Set up proper
triggering. Make sure the overshoot does not double trigger the counter. Set the counter to
period measure. Set PERCENT ENERGY dial to 100% and press TREAT button. The
reading should be 14.28 msec ± 5% which corresponds to 70 Hz. Set PERCENT
ENERGY dial to 50% and press TREAT button. The reading should be 25.00 msec ± 5%
which corresponds to 40 Hz. Set PERCENT ENERGY dial to 20% and press TREAT
button. The reading should be 50.0 msec ± 5% which corresponds to 20 Hz.
3.6

TEST STIMULUS DURATION

There are two ways to test stimulus duration. The more precise way uses an event counter
(many frequency counters are capable of event counting). The less precise way uses an
oscilloscope.
A) Connect an event counter across the dummy load (using the divider) and set to trigger
properly. Make sure the overshoot does not double trigger the counter. Set PERCENT
ENERGY dial to an appropriate setting and press the TREAT button. Note the counter
reading and check for correspondence to table 3.1. Repeat procedure for rest of the
settings.
SOMATICS, LLC
fig 3.5
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REV: 3.1 09/15/2015