Kinemetrics EpiSensor FBA ES-T, User Manual

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D
OCUMENT
301900, R
EVISION
D
50 E
PI
S
ENSOR
U
SER
G
UIDE
Table 11: Current requirements
Examples Quiescent
Dual
"
12V
Supply
Max Load
Dual
"
12V
Supply
Quiescent
Single 12V
Supply
Max Load
Single 12V
Supply
EpiSensor 1g low-power amplifier
2.5V single-ended output
12 mA 25 mA 65 mA 104 mA
EpiSensor 2g low-noise amplifier,
20V differential output
35 mA 70 mA 130 mA 270 mA
EpiSensor 0.25g low-noise
amplifier 20V differential output
35 mA 57 mA 130 mA 218 mA
Output Voltage
The EpiSensor output is user-selectable, as is the output amplifier. Select
the EpiSensor output that matches the recorder input. If possible use a
differential input connection for optimum performance. Configuring the
correct range and output is described in
Chapter 3 .
The output impedance of the EpiSensor is 50
%
to ensure the unit is stable
under capacitive loading from a long cable. Normally data loggers have an
input impedance of 100 k
%
or more, so the 50
%
output impedance is
insignificant.
Calibration Sequence
To produce a functional test sequence the recorder must control the Cal and
CCE line to the EpiSensor.
Even if the recorder cannot produce a functional test it is still very important
that these lines be held at the correct potential. The Cal line is not connected
to the sensor unless the CCE line is active, but to provide the best noise
performance it should not be left floating. We suggest that the CCE line be
grounded to power common when the calibration coil is not in use.
The CCE line drives a transistor that operates an analog switch that
connects the Cal line to the sensor module calibration coil. The transistor
will turn on the analog switches at voltages b5 to +12V. The
transistor is not activated at voltages below 0.5V. This means a CMOS
driver can drive the line or an open collector output pulled up to 12V.
A transistor-transistor logic (TTL) level will probably work if the sensor is
close to the digitizer.
It is very important that the CCE line is not enabled
when the calibration feature is not in use and that it is not powered when
the unit is not powered.
This is because the Cal line is connected to all the sensor coils during the
calibration sequence, which can result in both additional noise and cross
coupling between the sensors. The easiest way to prevent power conflicts
from the CCE line is to connect it to the power common or the –12V supply
of the EpiSensor.