Advertisement
OPERATION AND CHECKOUT
Operation
The C7046A,B,C Air Temperature Sensors consist of a
thermistor sensing element mounted in a tubular probe. They
are applied at various locations throughout single zone and
multizone duct systems. The negative temperature coefficient
(NTC) characteristic of the thermistor element causes its
resistance to decrease as the sampled air temperature
increases. This resistance shift is balanced with other system
sensor signals by appropriate system logic panels to stabilize
system control.
The C7046D Air Temperature Sensor consists of a platinum
thin film sensor element mounted in a tubular probe. It can be
applied at various locations throughout single zone and
multizone duct systems. The positive temperature coefficient
(PTC) characteristics of the platinum thin film element causes
its resistance to increase as the sampled air temperature
increases. This resistance shift is balanced with other system
sensor signals by the Excel 500 Control System.
Checkout
Allow the C7046 Air Temperature Sensor to soak in the air
moving through the duct or plenum for a minimum of five
minutes before taking a resistance measurement.
1. Disconnect the sensor leadwires from the associated
system components.
2. Connect an ohmmeter across the leadwires.
3. Assure nominal resistance measurements are in
accordance with the resistance/temperature curves
shown in Figs. 7, 8 and 9.
4. Reconnect sensor leadwires to associated system
components.
5. Check operation of the complete control system.
17000
16000
15000
14000
13000
12000
11000
10000
9000
8000
7000
6000
5000
4000
3000
2000
1000
10
20
30
40
-10
0
-5
5
TEMPERATURE (DEGREES)
Fig. 7. C7046A,C Sensor resistance vs. temperature.
3,000 OHMS
AT 77 F (25 C)
50
60
70
80
90
100
F
10
20
30
35
15
25
C
M17969
C7046A,B,C,D AIR TEMPERATURE SENSORS
120000
100000
80000
60000
40000
20000
0
20
30
40
-7
0
5
Fig. 8. C7046B Sensor resistance vs. temperature.
RESISTANCE
(OHMS)
1159
1141
1126
1111
1096
1081
1066
1051
60
65
55
13
15
20
Fig. 9. C7046D Sensor resistance vs. temperature.
5
22,800 OHMS AT
77 F (25 C)
50
60
70
80
90
100
110
10
15
20
25
30
35
40
45
TEMPERATURE (DEGREES)
1097 OHMS AT
77 F [25 C]
70
75
80
85
90
95
25
30
35
TEMPERATURE (DEGREES)
F
120
130
140
C
50
55
60
M17973
100
105
F
38
41
C
M2826
60-2350—8
Advertisement
