2012-005 Silicon Designs, Inc., 2012-005 Datasheet - Page 3

• Manufacturer Part Number: 2012-005
• Description: ANALOG ACCELEROMETER MODULE
• Manufacturer: Silicon Designs, Inc.

CABLE SPECIFICATIONS & LENGTH CONSIDERATIONS
The cable consists of four 26 AWG (7x34) silver plated copper wires with PTFE insulation surrounded by a braided shield. The
shield jacket is a PTFE tape wrap with a nominal outer diameter of 0.131”. Extending the model 2012's one meter cable is not
recommended. If you do decide to connect additional cable, we recommend you check each individual installation for oscillation
by tapping the accelerometer and watching the differential output for oscillation in the 20kHz to 50kHz region. If no oscillation
is present, then the additional cable length being used is OK for that particular device.
CONVERTING THE 2012's DIFFERENTIAL OUTPUT TO SINGLE ENDED
To achieve the highest resolution and lowest noise performance from your model 2012 accelerometer module, it should
be connected to your voltage measurement instrument in a differential configuration using both the AOP and AON output
signals. If your measurement instrument lacks differential input capability or you desire to use a differential input capable
instrument in single ended mode, then the circuit above can be used to preserve the low noise performance of the model
2012 while using a single ended type connection.
This circuit converts the ± 4 Volt differential output of the model 2012 accelerometer, centered at +2.5 Volts, to a single
ended output centered about ground (0.0 Volts). It provides the advantage of low common mode noise by preventing the
accelerometer’s ground current from causing an error in the voltage reading.
The op-amp should be located as close as possible to your voltage monitoring equipment so that the majority of the signal
path is differential. Any noise present along the differential path will affect both wires to the same degree and the op-amp
will reject this noise because it is a common mode signal. The op-amp type is not critical; a µA741 or ¼ of a LM124 can
be used. Both plus and minus supplies are needed for the op-amp to accommodate the positive and negative swings of
the single ended output. The same +5V supply can be used for both the op-amp and the 2012 or a higher voltage positive
supply can be used for the op-amp if you need a larger single ended output swing.
For this design, always set R
When R
obtain a ± 5 Volt single ended output, set R
centered at ground if R
The value of the optional capacitors C
range of interest. The cutoff frequency f
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1
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= R
2
= R
3
= R
4
2
, the gain equals 1 and the output swing will be ± 4 Volts single ended with respect to ground. To
and C
1
1
= R
are tied to ground; using some other fixed voltage for this reference will shift the output.
3
, R
1
2
and C
= R
0
(-3 dB frequency) for this single order low pass filter is given by:
4
2
and C
2
(C
/R
1
1
= C
= R
1
Model
f
= C
2
) can be selected to roll off the frequency response to the frequency
0
4
/R
=
2
[page 3]
3
. The gain of the circuit is then determined by the ratio R
= 5/4 = 1.25. The single ended output of the op-amp will be
2
π
2012
R C
1
2
1
Analog Accelerometer Module
Sep 07
2
/R
1
.