MTC-20/2S User Manual
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version 2.7
page 10
Internal SENSOR mode
In this mode the output voltage is controlled by the PI controller (PI [proportional-integral
controller system] activated). The temperature signal which is used for the control unit is
selected by the MODE switch.
The SENSOR A or SENSOR B position selects one of the internal thermometers
(SENSOR A or SENSOR B) which use a small semiconductor sensor. The measured
temperature is shown at the respective digital display unit (
2
or
6
, Figure 1
respectively, XX.X °C).
If no sensor is connected or if the sensor is damaged or short circuited the internal
shut-off unit disconnects the power output. This state is indicated by the red ALARM
LED (
3
or
7
, Figure 1 respectively) located just above the sensor connectors.
EXT. SENSOR mode
This mode can be used to connect an external thermometer. The calibration of the external
input (SENS. INPUT BNC, (
15
, Figure 1)) is 1 mV / °C. If this option is used the internal
ALARM circuit is disabled.
Modes of Operation Overview
DIRECT MODE:
output voltage is set directly by the DESIRED TEMP. °C control.
Internal SENSOR mode: output voltage is controlled by the PI controller using SENSOR A
or SENSOR B.
EXT. SENSOR mode:
output voltage is controlled by the PI controller using an external
thermometer.
POWER OUTPUT is always available at POWER OUTPUT, SENSOR A and SENSOR B.
3.6.
Setting the DESIRED TEMPERATURE
There are two ways to set the DESIRED TEMPERATURE:
1. The easiest way is to use the potentiometer DESIRED TEMP. / °C. The temperature
can be set with this potentiometer from +25.0 °C to +45.0 °C. If the MTC-20 leaves
this temperature window the internal shut-off unit disconnects the power output. This
could be the case if the sensor is broken or short-circuited.
2. If the user wants to have external control (e.g. with a computer system) or to set the
temperature to lower (<25 °C) values, the DESIRED TEMPERATURE can be set
using the COMMAND INPUT 10mV / °C connector (
10
, Figure 1). The COMMAND
INPUT is scaled 10mV / °C, i.e. +370 mV at this connector would set the DESIRED
TEMPERATURE to +37 °C.
Important
: The set value of the temperature is always the sum of the setting at DESIRED
TEMP. / °C potentiometer and the voltage at COMMAND INPUT 10mV / °C connector, i.e.
if DESIRED TEMP. / °C is set to +25.0 °C and the voltage at COMMAND INPUT 10mV /
°C is +150 mV the temperature will be set to +40 °C !!