System 350 A350P Electronic Proportional Plus Integral Temperature Control Product/Technical Bulletin
9
If a Y350R Power Module is used, select DC
volts on the DVM. Verify that the voltage is
between 16 and 38 VDC.
If an external DC power supply is used, select
DC volts on the DVM. Verify that the voltage is
between 22 and 29 VDC.
b. If the DVM reading is within the indicated
voltage range, select DC volts on the DVM
(DVM must be accurate to +/-0.01 VDC), and
connect the (+) lead to Terminal VDC and the
(-) lead to Terminal C.
If the DVM voltage is between 4.9 and
5.1 VDC, proceed to Step 2.
If the DVM voltage is above 5.1 VDC, replace
the A350P.
c. If the DVM voltage is below 4.9 VDC, check
the control using the following procedure.
Disconnect all loads from the A350P control.
(If in Direct Acting mode with power on, the
system will go to full output when the sensor is
disconnected. Thus, ensure that any loads are
disconnected
before
disconnecting the
temperature sensor.)
Disconnect the temperature sensor
completely, and recheck the DVM voltage.
If the DVM voltage rises to a value between
4.9 and 5.1 VDC, replace the sensor.
If the DVM voltage is still below 4.9 VDC,
replace the A350P control.
2. Check sensor for proper resistance at a given
temperature. (The resistance across the sensor
changes with the temperature of the sensor.)
a. Disconnect power from the A350P control.
b. Disconnect the sensor from the control and
measure the resistance across sensor leads.
c. When measuring the sensor’s resistance, use
an accurate thermometer to measure the
temperature at the sensor.
d. Refer to Figure 8 to determine the optimal
resistance for the measured temperature.
e. If the measured resistance varies substantially
from the optimal resistance for that
temperature, the sensor or wiring must be
replaced.
f.
If the sensor’s resistance conforms to the
chart in Figure 8, reconnect the sensor to the
control.
g. Reconnect power to the control.
Note:
The sensor reading indicated by the D350
may differ somewhat from thermometer
readings due to sensor tolerances, time
constants, thermometer accuracy, and other
factors.
°F
Temperature
260
240
220
200
180
160
140
120
100
80
60
40
20
0
-20
-40
500
700
900 1100
Resistance (Ohms)
1300 1500 1700 1900 2100
°C
120
100
80
60
40
20
0
-20
-40
Figure 8: Temperature vs. Resistance Chart for the
A99B Series Sensor
