Structure of the measuring amplifier

The measuring amplifier supplies the Wheatstone bridge with a stable and low-noise voltage. The (differential) output of the Wheatstone bridge is set to a signal level of e.g. 10 volts or 20 milliamps, or via a digital interface, e.g. USB, CANbus, EtherCAT, WiFi, Bluetooth, ... provided for further processing.

Figure 1 shows the basic structure of the analog measuring amplifier:



Figure 1: Block diagram of the measuring amplifier with analog signal processing

The measuring amplifiers of the series GSV-1 and GSV-11 have an analogue signal path. Zeroing is done by adding a voltage in the first amplifying stage. The "Gain", "Range" or "Input Sensitivity" can be adjusted via jumpers on some models (GSV-1H, GSV-1A, GSV-1A4, GSV-11H) to eg 2.0 mV/V, 1.0 mV/V, 0.5mV/V or 0.2mV/V. The filter is fixed in each order variant and dimensioned, for example, to a cutoff frequency (-3dB) of 250Hz, 2.5kHz, 10kHz for GSV-1 and 20Hz for GSV-11H.

The output resistance is 50 ohms at voltage output, the load at current output is 300 ohms.

Figure 2 shows the block diagram of the digital measuring amplifiers:


Figure 2: Block diagram of the measuring amplifier with digital signal processing

The measuring amplifiers of the series GSV-6K, GSV-6L, GSV-15 have an analogue output signal. The analogue output signal can be adjusted to the maximum input signal at rated load of the sensor "continuously" by the digital signal processing: at the output of the measuring amplifier, e.g. exactly 10V or 20mA displayed at rated load. The zero adjustment is also carried out in the digital part of the measuring amplifier.

The GSV-6 can also be used to configure the filtering of the output signal by adjusting the sampling frequency. The type of output signal (current or voltage and the offset at the analog output can also be set).

The GSV-15 has a fixed sampling frequency of 115Hz.

The measuring amplifiers GSV-2TSD-DI, GSV-2MSD-DI and GSV-8 have a "Cal" function at the input of the measuring chain: By pressing a "Short" or "Check" button (GSV-8), the bridge output (with a relay) is short-circuited. This function can be used to determine the deviation of the output signal of the Wheatstone bridge from 0 mV/V. By pressing the "Short" key during an automatic zero adjustment, the zero balance of the measuring amplifier can be reset.

The measuring amplifier GSV-8 has additional functions, such as a mechanism to trigger a step response to test the configurable IIR and FIR filters.