Datasheet

DATA SHEET
Technical changes reserved
0141 0316-115 07/2009
Thermocouple module
with digital I²C-Interface - THMOD-I²C
Application notes
In the scope of supply, a thermocouple type K is included for test pur-
poses, which is suitable in the range of Teon insulation up to approx.
250 °C. For higher application temperatures, the insulation must be
removed or for example, a metal sheathed thermocouple should be
used.
The operating voltage of 6 to 24 V is stabilised in the module to 5 V.
The internal voltage of 5 V also serves as the reference level for the
digital I²C-communication. Other options, for example, with 3.3 V or 5 V
operating voltage are also available as special models.
While connecting the measuring probes over longer routes, the I²C-
Bus, which is used externally out of the device, should not be used
internally, in order to avoid coupling of interferences to the device
internal communication. The EMV-guidelines are to be followed and
application of shielded lines are to be recommended.
By short time interruption of operating voltage, a RESET of the ASIC
can be caused. If there is a provision of switching off the operating
voltage, then the pullup resistance of the I²C-Bus must be connected
to the switched voltage.
Connection layout of the plugs
Pin Title Function
1 (white) VDD Operating voltage 6 ... 24 V
2 GND Ground
3 SDA Serial data I²C
4 SCL Serial counter I²C
5 --- not used
6 --- not used
I²C-Interface
The communication corresponds to I²C protocol. The default address
of the component is 0x78 and the component can always be commu-
nicated under this address. Additionally, a second address can also be
programmed during conguration ex factory, through which the sensor
can be addressed.
At the address 0x78, 4 Bytes can be read. The following assignment
is applicable:
Data
0x78 Byte_0 MSB Thermovoltage
Byte_1 LSB Thermovoltage
Byte_2 MSB Connector temperature
Byte_3 LSB Connector temperature
Scaling of measured values
Both the thermovoltage as well as the temperature of the connection
point are transferred as 15 bit value (bit 0 - 14). From the 15 bit mea-
sured value, the thermovoltage is used as 14 bit resolution, the least
signicant bit (0, 1) can be ignored. In case of temperature connection
point, the 12 bit resolution is used, the least signicant bit (0-2) can be
ignored. The most signicant bit (15) is always 0 during normal opera-
tion and in case of error, it is set to 1.
The following scaling is applied for measured values:
Thermovoltage Typ -300
Numeric value via I²C Interface 0x 0000...7FFF
dec. 0...32767
Physical value -12,500...20,268 mV
Measuring range 32,768 mV
Resolution 2 µV
Thermovoltage Typ -800
Numeric value via I²C Interface 0x 0000...7FFF
dec. 0...32768
Physical value -12,500...53,036 mV
Measuring range 65,536 mV
Resolution 4 µV
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