Publication No. 980972 Rev. B 850A/B User Manual
Chapter 2
Operation
The 850A/B Contact Chatter Detector contains ten contact monitors in a chassis
19 inches wide by 3-1/2 inches high and 8 inches deep.
The unit operates using either 117 or 234 Volts RMS power. The switch S1 next
to the transformer (cover must be removed to view, see Figure 2-1) is marked 117
and 234. Set S1 to the appropriate position for the power that is to be used.
Damage can be caused to the circuitry if S1 is in the 117 position and 234 V RMS
AC power is applied. With S1 set properly, apply the AC power and the unit is
ready to operate.
Current Setting
Before connecting any contact to the Contact Chatter Detector, set the current
that will flow in the contact. Damage could be caused if the current was set higher
than the contact current rating. The current is set between 0.1 to 11 millliamps
using the contact current dial and the X1–X0.1 switch to provide two ranges.
When the X1–X0.1 switch is in the X0.1 position the dial sets 0.1 to 1.1 milliamps
and the X1 position provides 1 to 11 milliamps. The current setting is for all ten
channels. To prevent damage to the contacts each channel voltage is clamped
below 3 Volts.
Time Interval Switch Settings
The Time Interval Switches set the time discontinuity can exist (in a NC contact)
before it is considered a FAULT, for a NO contact the opposite or closure for
longer than the set time interval would constitute a FAULT. The time interval can
be set from 1 to 999 microseconds or 1 to 999 milliseconds using the three digit
thumb switch in conjunction with the MICROSEC-MILLISEC switch. The accuracy
is the setting ±3 LSD. These switches should be set to the appropriate setting for
the contact or contacts being monitored.
Contact Connections and Switches
Connect the contact to be monitored to a channel input BNC (850A) or terminal
(850B). Set the Contact Switch to the required position NC if the contact is in the
closed position and NO if the contact is being tested in the open position.
Astronics Test Systems
Operation 2-1
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