Precision-digital PD6000 User Manual download pdf (Page 21)

Model PD6000 Analog Input Process Meter Instruction Manual

Switching Inductive Loads

The use of suppressors (snubbers) is strongly recommended when switching

inductive loads to prevent disrupting the microprocessor’s operation. The sup-

pressors 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:

Figure 11. 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 con-

firm 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.

Figure 12. Low Voltage DC Loads Protection

RC Networks Available from Precision Digital

RC networks are available from Precision Digital and should be applied to each

relay contact switching an inductive load. Part number: PDX6901.

Note:

Relays are de-rated to 1/14th HP (50 watts) with an inductive load.

Use a diode with a reverse

breakdown voltage two to

three times the circuit vol-

tage and forward current at

least as large as the load

current.

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Precision-digital PD6000 User Manual Page 21