The Smart Temperature Acquisition System
(SMTAS08) is an 8 channel temperature measurement system. It was designed
to get the best possible temperature measurement results with the SMT160-30
Smartec digital temperature sensors.
The SMT160 is a three-terminal integrated temperature sensor
with a duty-cycle-modulated square-wave output signal.
The SMTAS08 is equipped with a Microchip PIC16F876
An RS232 interface chip offers external serial communication
with the microcontroller.
In turn each of the sensors is powered by a corresponding
processor output. An analog multiplexer (74HC4051), which is controlled by
the microcontroller, selects one of the eight sensor outputs by connecting
it to the microcontroller input port. The input is then sampled to measure
the dutycycle for this sensor (represented by two counter values, t1 and
t2). This process is repeated for each of the sensors, after which the 8
values of t1 and t2 are sent to the RS232 port.
No power supply is needed.
Accuracy, TO18 model, 0.7 °C in the range from -30 °C to +100
°C and an accuracy of 1.2 °C from -45 to +130 °C.
See SMTAS04 acquisition board if
measurement of only 4 digital temperature sensors are required. The
SMTAS04 is also available with USB interface.
A demo Labview , a Visual Basic program and the Logsmart program is available
for download. All programs allow communication with the SMTAS08 board, (
Labview screen shot above).
The free LogSmart program writes the value of the temperature sensors to
a log file. This can be a symbolic link file, tab file or excel file. (Logsmart
screen shot below)
The PIC processor assembly program listing used on the SMTAS08 is
available for download on this page.