Setra System Model 141 - Manual (Page 2)

orient the diode correctly. This Zener diode protects the transducer circuit against high voltage
transients and against inadvertent application of excess voltages or reversed voltage. Note that the
Zener diode normally conducts up to 200 milliamperes satisfactorily but that excessive current drain will
cause the Zener diode to short-circuit internally, hopefully protecting the transducer from damage.
Should this happen, the Zener diode must of course be replaced before further use of the transducer.
MODEL 141B MUST NOT BE OPERATED WITH
EXCITATION VOLTAGE EXCEEDING 28 VDC
Model 141B accelerometer excitation power 10 VDC minimum and 28 VDC maximum. High voltage
may burn out the circuit. Installation of a protective Zener diode such as IN4752 across the excitation
power input leads is a good practice, taking care to orient the diode correctly. This Zener diode protects
the transducer circuit against high voltage transients and against inadvertent application of excess
voltages or reversed voltage. Note that the Zener diode normally conducts up to 30 milliamperes
satisfactorily but that excessive current drain will cause the Zener diode to short-circuit internally,
hopefully protecting the transducer from damage. Should this happen, the Zener diode must of course
be replaced before further use of the transducer.
CALIBRATION SIGNAL
Select an external R
CAL
and shunt the red lead through R
CAL
to the brown lead (-signal output).
An R
CAL
value is shown on the calibration certificate. Less conductive resistors produce a nearly
proportional decrease in calibration signal. Higher conductivity resistors produce a similarly
proportional increase in calibration signal.
THE CALIBRATED OUTPUT OF YOUR ACCELEROMETER
Your accelerometer was factory-calibrated on a centrifuge at a precise excitation voltage reported on the
calibration certificate. The accelerometer output voltage was measured into open circuit (10 megohms).
The output impedance of the 141 accelerometer is 9K ohms (nominal).
Loading effect on the output does not appreciably change the linearity or thermal behavior of the
transducer. The output into heavy loads may be calculated by assuming simple voltage divider action.
The sensitivity is approximately proportional to the excitation voltage.