P
AGE
10
Contacts - Arcing may occur across contacts when the contact opens and closes. This
results in electrical noise as well as damage to the contacts. Connecting a RC network
properly sized can eliminate this arc.
For circuits up to 3 amps, a combination of a 47 ohm resistor and 0.1 microfarad capacitor
(1000 volts) is recommended. For circuits from 3 to 5 amps, connect 2 of these in parallel.
See Figure 2-3.
FIGURE 2-3
2.2.2 SENSOR PLACEMENT (Thermocouple or RTD)
Two wire RTD's should be used only with lead lengths less than 10 feet.
If the temperature probe is to be subjected to corrosive or abrasive conditions, it should be
protected by the appropriate thermowell. The probe should be positioned to reflect true
process temperature:
In liquid media - the most agitated area.
In air - the best circulated area
A.C.
MOV
R
Inductive
Load
C