Dwyer LCR10 - Manual (Page 8)

LCR10 IOM Page 8 of 20 April, 2003
2-6 Sensor Installation Guidelines
Proper sensor installation can eliminate many problems in a control
system. The probe should be placed so that it can detect any temperature
change with minimal thermal lag. In a process that requires fairly constant
heat output, the probe should be placed close to the heater. In a process
where the heat demand is variable, the probe should be close to the work
area. Some experiments with probe location are often required to fi nd this
optimum position.
Proper sensor type is also a very important factor to obtain precise
measurements. The sensor must have the correct temperature range to
meet the process requirements. In special processes the sensor might
need to have different requirements such as leak-proof, anti-vibration,
antiseptic, etc.
Standard thermocouple sensor limits of error are 2 degrees C (4 degrees
F) or 0.75% of sensed temperature (half that for special limits of error) plus
drift caused by improper protection or an over-temperature occurrence.
This error is far greater than recorder error and cannot be corrected at the
sensor except by proper selection and replacement.
In order to connect the probe input device to the recorder, you must fi rst
gain access to the microprocessor PC board that is mounted to the back
of the chart plate.
CAUTION! DO NOT TOUCH the terminals of the transformer
while the recorder is connected to the main AC power supply.
To avoid the risk of possible electric shock, unplug or disconnect
the recorder from the main power supply before attempting to
open the recorder. Also, disconnect the 9 Volt battery to avoid
damaging the recorder and draining the battery.
The recorder has a hinged chart plate held in place by two (2) screws
located on the right hand side of the chart plate. Remove these two
screws and open the hinged chart plate. See Figure 2-5 (pg. 13) for screw
location.