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BT32i Differential Voltage sensor User’s Guide
Short description
The Differential Voltage sensor BT32i is designed for measuring voltages in the range
between -‐500 and 500 mV. The sensor is a signal amplifier with a wide frequency
range, which can be used to measure small voltages in AC and DC circuits.
The sensor has differential inputs, which means that measurements can be done
directly across circuit elements without the constraints of common grounding. It can
be used to measure positive, as well as negative potentials. It has two banana (4-‐
mm) plugs for easy connection.
The sensor should be connected parallel to a circuit element. It measures the
potential difference between the V
+
-‐ red plug and the V
-‐
-‐ black plug. The measured
voltage goes through an amplifier unit and the output of the sensor is adjusted to
the range of
±
7.5V. The sensor is provided with over-‐voltage protection and voltages
up to
±
50V (related to ground) will not damage the sensor. It never can be used for
higher voltages.
The Differential Voltage sensor can be directly connected to analog BT inputs of the
CMA interfaces. The sensor cable BT -‐ IEEE1394 needed to connect the sensor to an
interface is not supplied with the sensor and has to be purchased separately (CMA
Article BTsc_1).
Sensor recognition
The Differential Voltage sensor has a memory chip (EEPROM) with information about
the sensor: its name, measured quantity, unit and calibration. Through a simple
protocol this information is read by the CMA interfaces and the sensor is
automatically recognized when it is connected to these interfaces. If your Voltage
sensor is not automatically detected by an interface you have to manually set up
your sensor by selecting it from the Coach Sensor Library.
Calibration
The CMA Current sensor BT32i is supplied calibrated. The output of the sensor is
linear with respect to the input voltage. The supplied calibration function is:
V
in
(mV) = 78.125 * V
out
(V) – 0.47 where V
in
= V
+
-‐ V
-‐
The Coach program allows selecting the calibration supplied by the sensor memory
(EEPROM) or the calibration stored in the Coach Sensor Library. For better accuracy
the pre-‐defined calibration can be shifted.
For even more accurate measurements a new user calibration (a standard, simple 2-‐
point calibration) can be performed in Coach using known voltages.
