Delta OHM HD 778TR1 Manual De Instrucciones página 4

CHOOSING THE TYPE OF THERMOCOUPLE
The transmitter accepts four types of thermocouples. The set thermocouple is
indicated by the number of led blinks when the power is turned on.
Number of led blinks
1
2
3
4
The transmitters are supplied with the default setting of: K thermocouple
and 4...20mA = 0...1000°C range.
The user can modify the type of thermocouple and the range of functioning with
the following procedures.
Note: after modifying the type of thermocouple, the range of functioning
must be programmed.
HD778TR1 and HD978TR1
When turning on the transmitter, the led blinks for a certain number of times
equal to the type of thermocouple previously set.
In order to modify the setting, turn the transmitter off and back on again keeping
the button pressed down.
This opens the program for selecting the type of thermocouple. If the K thermo-
couple has been selected the led blinks once.
If you release the button and press it down again within 10 seconds, the led will
blink twice: the J thermocouple is now selected.
If you press the button again within 10 seconds, the led will blink 3 times: the
T thermocouple is now selected.
If you press the button again within 10 seconds, the led will blink 4 times: the
N thermocouple is now selected.
If you press again the button within 10 seconds, the led will blink once to indi-
cate that the K thermocouple has been selected again and the cycle repeats.
In order to save the selected thermocouple, do not press the button and wait 15
seconds. As the transmitter saves the type of thermocouple, the led blinks for a
number of times equal to the type of thermocouple selected.
If you modified the type of thermocouple the range of functioning must be
reprogrammed. See the paragraph entitled "PROGRAMMING THE RANGE
OF FUNCTIONING".
HD978TR2
This transmitter is fitted with a dual dip-switch for the selection of the thermo-
couple type. The selection must be made before turning it on and it is set when
the device is turned on: a dip-switch change does not produce any effect when
the device is powered on until the next time it is turned off and on.
Procedure:
With the device turned off, select the type of thermocouple by setting the
switches as shown in the following figure.
1 2 1
ON ON
Tc = K Tc = J
When powering the transmitter, the led blinks for a number of times equal to the
type of thermocouple previously set.
If you modified the type of thermocouple the range of functioning must be
reprogrammed. See the paragraph entitled "PROGRAMMING THE RANGE
OF FUNCTIONING".
Type of thermocouple
K
J
T
N
2 1 2 1 2
ON ON
Tc = T Tc = N
PROGRAMMING THE RANGE OF FUNCTIONING.
The HD778TR1, HD978TR1 and HD978TR2 transmitters are supplied with
a default setting of: K thermocouple and 0...1000°C range. The user can set
a different range according to his requirements with a minimum span of 50°C.
The correspondence between the read temperature and the output current can
be direct (e.g. 4mA = 0°C and 20mA = 1000°C) or inverse (e.g. 4mA = 1000°C
and 20mA = 0°C).
Avail yourself of the following programming tools:
• 9...30 Vdc direct current power source,
• Thermocouple gauge,
• Copper connection cables,
• Precision ammeter with 0...25 mA minimum range.
RS232C
HD778-TCAL
RED: +
mV
OUTPUT
BLACK:
I
In place of the thermocouple gauge, it is possible to use the HD778-TCAL Delta
Ohm. This device must be connected to the PC's serial port, and by using the
special software it automates all the steps described below for the programmed
range of functioning.
If you have a thermocouple gauge then the steps are as follows:
To set the type of thermocouple proceed as described in the "CHOOSING THE
TYPE OF THERMOCOUPLE" paragraph.
The voltage values generated by the gauge must not be balanced.
The set up process must be carried out with the device already turned
on.
Set up the gauge for the desired type of thermocouple (K, J, T o N); connect the
gauge to the transmitter's thermocouple input, according to its polarity. (Pay
attention to the polarity.)
Set the gauge so that it generates the voltage corresponding to the temperature
at 4mA, and wait 30 seconds until the voltage stabilizes. The table Tab. 1
reports the voltages generate by the HD778-TCAL gauge according to the
type of thermocouple corresponding to the temperature value.
Press and keep the button pressed until the led starts blinking. Release the
button. The device acquires the first value of the transmitter work range,
and the led continues blinking. The tool now waits for the second data of
the end of scale range.
Set the gauge so that it generates the voltage corresponding to the temperature
at 20mA.
Press and keep the button pressed until the led stops blinking.
Release the button and wait 20 seconds, without modifying the gauge data,
so that the transmitter memorizes the calibration data and is ready to func-
tion normally. The operation is complete when the led blinks once.
The device has acquired the second point corresponding to the range you wish
to configure and starts to function normally.
The minimum span value accepted by the device is 60°C. If, after entering
the first value T1 of the range, the user tries to enter a second value T2 with
|T2-T1|<50, the device does not accept it and remains in the waiting status
with the led continuing to blink.
HD778-TCAL is provided with its own software. After it is connected to a
PC serial port by the programmer, the operator can follow the instructions
on the screen to configure the transmitter.
4...20 mA
<
PROGRAMMING
SWITCH
�
POWER
SUPPLY
Vdc
9...30 Vdc
�
RED LED
mA