Instructions
UM-0085-B09 DT80 Range User Manual Page 377
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• In the diagram, the two CEM20s have been assigned addresses 1 and 2. However any addresses could have
been chosen. The only rule is that a CEM20 with address n must have its analog output connected to analog
input n on the DT80.
CEM20 Addresses
CEM20s are identified by their address, which is set using the 4-way DIP switch on the end plate of the CEM20.
Each CEM20 must be set to a unique address before installation.
A CEM20's address determines where its analog output should be connected and how its channels should be
referenced. For example, a single CEM20 could be attached to a DT80 and set to address 5. This CEM20 would then
connect to analog input 5 on the DT80, and its channels would be referred to as 501, 502 etc.
The following table shows the required switch settings for each CEM20
CEM20 Address
Switch 1
Switch 2
Switch 3
Switch 4
1
-
-
-
ON
2
-
-
ON
-
3
-
-
ON
ON
4
-
ON
-
-
5
-
ON
-
ON
6
-
ON
ON
-
7
-
ON
ON
ON
8
ON
-
-
-
9
ON
-
-
ON
10
ON
-
ON
-
11
ON
-
ON
ON
12
ON
ON
-
-
13
ON
ON
-
ON
14
ON
ON
ON
-
15
ON
ON
ON
ON
16
-
-
-
-
Powering the CEM20
The recommended method of powering the CEM20 is to use the switched 12V power output on the DT80, as shown in
Figure 160. This output is capable of powering up to 15 CEM20 units.
By default, the DT80's 12V output will only be switched on during execution of a schedule containing CEM20 channels.
Other modes of operation are possible, however, and are selected using parameter P28, as described in Controlling 12V
Power Output (P290). In particular:
• set
P28=0 (default) to switch CEM20 power on and off as required. This minimises power usage.
• set
P28=1 and P21=1 to keep the CEM20s and the DT80's analog measurement system powered up
continuously. This will obviously use more power but will avoid the 50ms "warm up" delay that the DT80 inserts
when switching on either or both of these power supplies.
• set
P28=3 if the CEM20s are independently powered using an external power supply. The DT80's 12V output
may then be used to power other equipment if required and manually controlled using
PWR12V=1.
Note: that if the CEM20s are externally powered then a regulated 12V ±5% supply is required.
Accessing CEM20 Channels
CEM20 channels are numbered in the same way as regular channels, but with the CEM number as the hundreds digit.
Thus the first CEM20's channels are numbered from 101 to 120, the second from 201 to 220 and the sixteenth from
1601 to 1620. So to measure a thermocouple connected to the + and – terminals on first analog input channel on CEM20
#1 you would enter 101TK – as shown on the wiring diagram.
Channel sequences (see Channel Number Sequence (P34) can cross CEM boundaries. For example,
RA1M 119..203V
is equivalent to
RA1M 119V 120V 201V 202V 203V
Likewise, an array of 86 isolated thermocouples connected as per Figure 173 could be read using:
RA1M 3..220TK 3*..220*TK