Switching Inductive Loads; F4 Digital Input Connections; 4-20 Ma Output Connections; Analog Output Power Supply - Ametek DDMC Instruction Manual

DDMC Analog Input Process Meter / Controller

Switching Inductive Loads

The use of snubbers to suppress electrical noise is
strongly recommended when switching inductive
loads to prevent disrupting the microprocessor's
operation. The snubbers also prolong the life of the
relay contacts. Suppression can be obtained with
resistor-capacitor (RC) networks assembled by the
user or purchased as complete assemblies. Refer to
the following circuits for RC network assembly and
installation:
C
R

Figure 17. AC and DC Loads Protection

Choose R and C as follows:
R: 0.5 to 1 Ω for each volt across the contacts
C: 0.5 to 1 µF for each amp through closed
contacts
Notes:
1. Use capacitors rated for 250 VAC.
2. RC networks may affect load release time of
solenoid loads. Check to confirm proper
operation.
3. Install the RC network at the meter's relay screw
terminals. An RC network may also be installed
across the load. Experiment for best results.
Use a diode with a reverse breakdown voltage two to three
times the circuit voltage and forward current at least as large
as the load current.

Figure 18. Low Voltage DC Loads Protection

RC Networks (Snubbers)
Available from AMETEK
RC networks are available from AMETEK and should
be applied to each relay contact switching an
inductive load.
Note: Relays are de-rated to 1/14th HP (50 watts)
with an inductive load.

F4 Digital Input Connections

A digital input, F4, is standard on the meter. This
digital input should be connected with a normally
open contact across F4 and COM, or with an active
low signal applied to F4. It can be used for remote
operation of front-panel buttons, to acknowledge/reset
relays, or to reset max/min values. See Function Keys
& Digital I/O Available Settings on page 41 for a
complete list of capabilities.
C
R

4-20 mA Output Connections

Connections for the 4-20 mA transmitter output are
made to the connector terminals labeled mA OUT.
The 4-20 mA output may be powered internally or
from an external power supply.

Analog Output Power Supply

The internal 24 VDC power supply powering the
analog output may be used to power other devices if
the analog output is not used. The I+ terminal is the
+24 V and the R terminal is the return.
Figure 21. Analog Output Supply Powering Other
17

Figure 19. F4 Digital Input Connections

Figure 20. 4-20 mA Output Connections

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