Instructions

UM-0085-B09 DT80 Range User Manual Page 322
RG
IC3 – LM35-Series Inputs – full temperature range
This wiring configuration biases the negative terminal of the device to allow negative temperatures to be read. Refer to
the manufacturer's data sheet for more details.
Figure 148: Wiring for LM35 series input – full temperature range
To measure
Use the command
temperature
1LM35
Other Wiring Options
Shared input configurations and/or external power supplies (as per the wiring configurations for Voltage) can also be
used to allow more sensors to be measured per channel.
For example, the configuration shown in V1 – Shared Terminal Voltage Inputs (P305) could be used to allow three
externally powered LM35s to be measured on the one channel. That is, an external 4-30V dc supply powers the three
sensors’ + and – terminals, with the – terminals also connected to the DT80’s # terminal. The three out terminals would
then connect to the DT80’s *, + and – terminals. These sensors could then be read using
1*LM35(N), 1+LM35(N)
and
1-LM35(N) respectively. Note that in this case the N channel option is required in order to disable the default
voltage excitation output on the * terminal.
Temperature – LM135 Series IC Sensors
LM135 series sensors are 2-terminal zener diode based sensors which produce a voltage output that is proportional to
absolute temperature. Operating current is typically 0.5 – 5mA.
Channel Types
The following channel types are supported:
Channel Types
Description
Range
LM135
10mV / K -55 – +150 °C
LM235
10mV / K
-40 – +125 °C
LM335
10mV / K
-40 – +100 °C
Channel Options
The following channel options are sometimes used when measuring LM35 series devices:
• the excitation options specify how the sensor is powered:
V (use internal 4.5V voltage source; default), E
(external supply connected to EXT* terminal) or
N (external supply).
•
MDn (measurement delay) specifies that the DT80 should wait n ms (default 10ms) after selecting a channel
before starting the actual measurement. This can be useful in conjunction with the
E or V option, as it allows the
sensor some time to stabilise after power is applied to it.
•
GLx, ESn, as for voltage measurements
• the channel factor specifies a voltage divider value.
Note: A 2:1 voltage divider is normally used to ensure that the output of the sensor stays within the DT80's 3V input range. The default
channel factor is therefore 2.0 for these channel types. If a different voltage divider ratio is used then an appropriate channel factor must
be specified, e.g. if there is no divider then specify
1LM335(1).