Watlow EZ-ZONE ST - Manual (Page 21)

Ó
Warning:
Use National Electric (NEC)
or other country-specific
standard wiring and safety
practices when wiring and
connecting this controller to
a power source and to elec-
trical sensors or peripheral
devices . Failure to do so may
result in damage to equip-
ment and property, and/or
injury or loss of life .
NOTE: To prevent ground
loops, isolation needs to be
maintained from input to out-
put when using switched DC
or analog process outputs .
CAUTION: Always mount the
controller with the heat-sink
fins aligned vertically .
NOTE: Terminals L4 and
A1 on the limit connector
are jumpered at the factory
to complete the contactor
circuit . Additional switches
may be wired in series to the
terminals .
Ó
WARNING: If high voltage is
applied to a low-voltage con-
troller, irreversible damage
will occur .
Watlow EZ-ZONE ® ST • 19 • Chapter 2 Install and Wire
Input 2 Thermocouple
-
+
S2
R2
Slot A
• 20 kΩ maximum source resistance
• >20 MΩ input impedance
• 3 microampere open-sensor detection
• Thermocouples are polarity sensitive. The negative lead (usually
red) must be connected to S2.
• To reduce errors, the extension wire for thermocouples must be
of the same alloy as the thermocouple.
ST _ L - _ _ _ _ - _ _ _ _ (limit)
Input 2 RTD
2-wire
S2
R2
S1
S3
Slot A
3-wire
T2
S2
R2
S1
S2
S3
Slot A
• platinum, 100 and 1,000 Ω @ 0°C
• calibration to DIN curve (0.00385 Ω/Ω/°C)
• 20 Ω maximum lead resistance
• RTD excitation current of 0.09 mA typical. Each
ohm of lead resistance may affect the reading by
0.03°C.
• For 3-wire RTDs, the S1 lead (usually white) must
be connected to R2.
• For best accuracy use a 3-wire RTD to compensate
for lead-length resistance. All three lead wires must
have the same resistance.
ST _ L - _ _ _ _ - _ _ _ _ (limit)
Input 2 Process
-
+
S2
R2
volts
Slot A
-
+ T2
S2
amperes
Slot A
• 0 to 20 mA @ 100 Ω input impedance
• 0 to 10VÎ (dc) @ 20 kΩ input impedance
• 0 to 50 mVÎ (dc) @ 20 kΩ input impedance
• scalable
ST _ L - _ _ _ _ - _ _ _ _ (limit)