Io
SENSOR
Appendix A Connector Pinouts
SMT-200 Operations and Technical Manual 2.00/R1
91
A.5
Smartec Temperature Sensor
The Smartec temperature sensor is a solid state device that can be fed directly to an input line of a
microcontroller without the need for A-D conversion circuitry. Operating from a 5 V supply it provides a
duty modulated square wave on a single terminal. By averaging the output and comparing the time
spent at both high and low logic levels an accurate figure for the temperature can be found.
There are two Smartec temperature sensors that can be used for string temperature. The first is
located inside the Bendix geophone cable connector. The Bendix geophone connector is not used
with the docking station so in this case the external Smartec sensor is used. This plugs into the rear of
the Docking Station via the RJ-11 connector.
The Smartec temperature sensor is there to measure the
string temperature
. For the Smartec to
correctly measure the string temperature there should not be a large temperature differential between
the SMT-200 and the string being tested. In cases where there is a large difference, such as testing
inside a building when the strings are outside, it is advisable that the Smartec should be taken out of
the Bendix and mounted on a flying lead. The sensor can then be left close to the string under test to
give an accurate indication of string temperature.
If the temperature readings become unstable after the Smartec is mounted on the flying lead there
could be noise being picked up on the lead. If this is the case a simple filter circuit, as shown above,
should eliminate any pickup.
R1 (1K
Ω
)
C2 (0.1
µ
F)
Pin H
Pin J
Pin G
C1 (1 to 5
µ
F)
Gnd
V+
Ext
Viewed from
pin side
Tested to 40 meters
Smartec sensor mounted inside
