Troubleshooting Section:
Standard Temperature vs. 4-20mA Temperature
Sensors
As a quick troubleshooting guide for any of the 4-20 mA
Temperature Sensors, the following voltages can be seen at the
4-20 mA Input terminals TB1 thru TB12 (voltages as measured
between pin 2 Signal and pin 3 Analog Ground), corresponding
to the following standard temperatures:
Fº
Cº
mA
TBx Vdc
248
120
20.000
9.60
212
100
18.000
8.64
175
79.44
15.944
7.64
160
71.11
15.111
7.25
100
37.78
11.778
5.65
80
26.67
10.667
5.11
70
21.11
10.111
4.85
60
15.56
9.555
4.58
32
0
8.000
3.85
0
-17.78
6.222
2.99
-40
-40
4.000
1.92
‘Out-of-Range’ Sensor Detection
1) A 4-20 mA out-of-normal-range Temperature Sensor
Detection feature works as shown in the table below:
Temperature
Sensor’s Input
Current Range
Message shown
on 3-digit
LED Display
Type of Alarm
3.9mA to
20.1mA
N.A. (Live
Temperature)
N.A.
(Green zone.)
20.83mA
or higher
CLS
(Closed Circuit)
Red_Alarm
20.1mA to
20.83mA
HI
(High_mA)
Red_Alarm
1.0mA to
3.9mA
LO
(Low_mA)
Yellow_Alarm
7
1.0mA or
lower
OPn
(Open Circuit)
Yellow_Alarm
7
Note
7
: Because the ‘out-of-range’ Temperature Sensor LO and
OPn cases have 4-20mA signals less than 3.9mA, they are
not
Var12
and
Var13
over-temperature setpoint violations,
(but rather would be under-temperature cases). Because
the ES1 monitors for over-temperature behavior and not
under-temperature behavior, these cases are not outright
temperature violations. However, the Temperature Sensor
LO and OPn cases are treated as ‘Yellow_Alarm’ events
because the effected sensor could be programmed for the
BIAS setpt feature. And if a sensor goes ‘out-of-range’,
then the user needs to know this.
A) If a Temperature sensor fails as ‘LOW_mA’ or ‘Open_ckt’,
then its 3-digit display shows the “LO” or “OPn” message
respectively, and it alarms with its discrete Yellow-LED /
Yellow-Lightstack-Relay / Speed-Temperature-Warning-
Relay /Horn-Relay.
Also in this situation the opposite side companion sensor
does NOT go into a BIAS Setpt ‘Yellow_Alarm’ as a
BIAS response, for code is in place to see that the first
sensor failed. Because of this the second sensor does
NOT compare to a ‘out-of-range’ sensor.
B) If a Temperature sensor fails as ‘HI_mA’ or ‘Closed_ckt’,
then its 3-digit display shows the “HI” or “CLS” message
respectively, and it alarms with its discrete Red-LED / Red-
Lightstack-Relay / Speed-Temperature-Shutdown-Relay /
Horn-Relay.
Note: Since the ‘HI’ and ‘CLS’ cases have 4-20 mA signals
exceeding 20.1 mA, these cases must be treated as
over-temperature “Red_Alarms’.
C)
Concerning the Temperature displays and ‘out-of-range’
sensor latching:
During any ‘out-of-range’ Temperature Sensor ‘Yellow_
Alarm’ or ‘Red_Alarm’ (the OPn, LO, HI, or CLS cases),
the corresponding 3-digit LED temperature display ‘latches’
the most recent message, and will not automatically
return to showing ‘live’ temperature values (even if the
sensor ‘recovers’). This means that once an ‘out-of-range’
Temperature Sensor has been detected, the corresponding 3-
digit LED display will show the most recent message. This
allows the ES1 to show if a Temperature Sensor’s condition
goes from bad to worse, such as a LO case turning into an
OPn case, or a HI case turning into a CLS case, and vice
versa. To return the 3-digit LED temperature display to show
‘live’ temperatures, the user must manually acknowledge the
alarm by giving a ‘Silence_Horn/Alarm_RESET’ command.
2) If an analog input is programmed as a ‘Contact-Closure’
input by
Var11
, then the 3-digit messages shown are SAF,
ALr, or bAd.
For ‘Contact-Closure’ sensors the SAF and ALr are normal
valid messages, and the bAd message is used for invalid
sensor indication. See
Var11
Belt_Alignment_Sensor_Type_
Select section for details.
(Section continued on next page).
Free Catalog and Application Assistance
1.800.328.6170
Website: www.electro-sensors.com
990-005500 Revision D
11
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