User's Manual

MicroStrain, Inc.
Single Ended Input Channel
The SG-Link® OEM has one single ended input channel. This channel will
accommodate most 0-3 volt DC analog output sensors including accelerometers, pressure
sensors, geophones, temperature sensors, inclinometers and the like.
The SG-Link® OEM can provide +3 volts DC up to 50 mA to the sensor. Alternatively,
the sensor can be powered with +3 volts by any external constant source. In this case, the
current draw of the sensor will not compromise the SG-Link® OEM, i.e., it may exceed
50 mA.
Typical wiring to the SG-Link® OEM would follow these patterns. Please refer to the
Terminal Strip section for more details.
• If the sensor is to be powered by the SG-Link® OEM:
o Sensor ground lead to either pin 4 or pin 7
o Sensor signal lead to pin 6
o Sensor power lead to pin 1
• If the sensor is to be powered externally:
o Sensor ground lead to either pin 4 or pin 7
o Sensor signal lead to pin 6
The 3 volt signal is digitized by the SG-Link® OEM’s 12-bit A/D converter, creating a 0
to 4096 ‘bit’ digital range. As explained elsewhere, the Agile-Link™ system operates
digitally by resolving all sensor voltages to ‘bits’, transmitting the bits by radio to the
base station, carrying the bits into host software, and finally returning these bits to volts
at the software level. 0 volts = 0 bits, 2048 bits = 1.5 volts, 4096 bits = 3 volts, and so
forth. To state it as a formula: 3 Volts / 4096 bits = 0.000732 volts per bit. The volts
recreated on the host side can be further processed into engineering units by using the
scaling provided by the sensor manufacturer. Agile-Link™ software provides an on-
board function (Custom Formula) which allows for engineering units to be output and
displayed directly from the software if the manufacturer’s scaling formula is linear.
Polynomial scaling, non-linear scaling, and so forth will have to be dealt with on a post-
processing basis by the user.
In some case, users may want to use sensors which require 5 volt (or more) excitation. A
voltage divider can be employed between the sensor and the SG-Link® OEM terminal
strip to facilitate a 3 volt input. Caution should be exercised in such cases, as any
inherent signal noise will be amplified.
The SG-Link® OEM can not be used to measure sensors which output negative voltage.
The SG-Link® OEM should not be used with sensors with an impedance of greater than
5000 ohms.
A great way to become familiar with your new equipment is to take 15 minutes and
connect your SG-Link® OEM to the SG-Link® Tester Board. The SG-Link® Tester
Board, a precision instrument designed and manufactured by MicroStrain, incorporates a
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