xiii
Model TA502A
Quick Start Guide
External Relay Circuit
Clamping Diode
+
-
-
+
External Logic Interface
-
+
External Test Circuit
(TTL,CMOS,HTL)
Voltmeter
R
R
*
*
*
*
*
*
*
3 to 35VDC
3 to 35VDC
3 to 35VDC
NOTE:
Only one Field Transmitter may be connected to a Model TA502A. 4-
conductor cable is recommended if cable length is greater than 400 ft. See
Device Instruction Manual for connecting other Field Devices.
NOTE:
Many new devices have HART installed. For these devices the HART option
should be disabled (see individual device manual for instruction) when
interfacing with the TA502A.
Wire Outputs of Model TA502A
Inductive loads (bells, buzzers, relays, etc.) on dry relay contacts must be clamped
down. Unclamped inductive loads can generate voltage spikes in excess of 100 volts.
Spikes of this magnitude may cause false alarms and contact damage. Figure 7
shows the recommended relay protection circuits for AC and DC loads, respectively.
Figure 7: Relay Protection Circuits
The electrical rating for all open collector outputs is 100 mA @ 35 VDC. Figure 8
illustrates some typical open-collector external circuits.
Figure 8: External Test Circuits for Open Collectors
+
-
DC Control
Voltage
General Purpose Rectifier Diode,
1N4005 or Equivalent (Note Polarity)
Switched Load Coil
Bell, Buzzer, Relay,
Contactor, Solenoid
Valve, etc.
Protection circuit for relay contacts when switching a DC load.
Protection circuit for relay contacts when switching an AC load.
Valve, etc.
Contactor, Solenoid
Bell, Buzzer, Relay,
Switched Load Coil
Metal Oxide Varistor Rated for 150 VRMS,
Voltage
117 VAC Control
General Electric V150LA20A or Equivalent
