TM Page 15
3.3.1
TX35D/1/IFM Input Connections & Scaling
Input sensitivity of the transmitter input is set by a sending a command from the RE3D demodulator unit. This sets the gain
of the input amplifier as required by sending a command over the inductive power supply. Signal source offsets can also be
removed by the programmable amplifier, this again is controlled by the RE3D.
3.3.2
TX35D/1/IFM Calculation of Shunt Calibration Resistor "Rcal"
Two solder pins P5 and P6 are provided for the incorporation of a user fitted shunt calibration resistor (Rcal). The shunt
calibration facility is incorporated into the input stage and is activated by a command from the RE3D. A shunt calibration
resistor is connected across one arm of the strain gauge input circuit for a period of 10 seconds, this is either a DC or AC
signal at various frequencies. The shunt calibration resistor is user fitted across two solder pins. The micro-controller in the
transmitter switches the resistor between "0VEX" and "-SIG" pins for 10 seconds. This feature is mainly suitable for
inductively powered transmitters, since the command can be sent whilst the shaft is rotating, providing a "Remote
Calibration" facility. Required value for the calibration resistor Rcal, may be calculated from the following equation. The
calculation can also be done using the Strain Tx Setup – Cal Resistor menu in the RE3D.
Transmitters with 3.0Ex
For example;
3.3.3
TX35D/1/IFM Specifications
Input:
1 channel full bridge strain gauge input. "Instrumentation Amp" input, operating at 1.5V
common-mode (set by strain gauge bridge common-mode). Series and common-mode
input resistance 20 M ohms. Input bias current 1 nA. Input sensitivity set by remote
programming using the RE3D. Range 0.1 mV to 500 mV full scale.
Bridge Excitation Supply:
3.0VDC ±1% over full operating temperature range. Voltage temperature coefficient
typically 20 ppm / °C. Maximum bridge output curre nt 40 mA. Short circuit protected.
Zero Shift with Temperature:
Typically 0.03 %/°C.
Resolution & Accuracy:
15 bits plus sign, 0.1% full range.
Operating Temperature Range:
-50 °C to +120 °C. Ext ended range to special order.
Power Requirement:
3.3 - 12 VDC @ 9 mA plus bridge current.
Dimensions:
35mm x 20mm x 5mm
Weight:
Transmitter only; 6 grams.
Construction:
Encapsulated in high temperature epoxy resin
750 x Gauge Resistance
Required Signal in mV
Calibration Resistor in Ohms =
- (0.5 x Gauge Resistance)
750 x 350
2 mV
- (0.5 x 350)
Calibration Resistor in Ohms =
= 131,075 ohms
Содержание TX31D/1/IFM
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