IfTA ChargeSignalGenerator: The Charge and Signal Generator
Test & Calibrate Measurement Chains
The IfTA ChargeSignalGenerator (CSG) is a charge and signal generator for testing piezoelectric measurement chains. The light and handy device can simulate sensors, e.g. high temperature sensors for pressure and acceleration.
The intuitive operation is carried out via function keys and a 2.7 inch display. Thanks to the battery supply, display back lighting and carrying strap, the charge generator can also be used in places that are dark and difficult to access. For differential charge signals a Lemo connection is available that is identical to the common sensors. Other variants are covered by optional adapters.
Frequency and amplitude of the output signal are freely determined by the user. In addition to the sinusoidal waveform, the simulator also offers an asymmetric waveform to check the polarity of the cabling of a measurement chain. The synchronous voltage output can also be used to determine transfer functions, e.g. of charge amplifiers.
Through precise digital synthesis, the IfTA ChargeSignalGenerator offers high accuracy and can also be used for calibration. Optionally, the charge and signal generator can be calibrated traceable to the national reference standard (DIN EN ISO / IEC 17025).
Compact and lightweight design, network-independent battery power and user-friendly operation save important time during commissioning. Check your measurement chains and measuring instruments yourself and make sure that they function correctly. This saves problems and time, as components do not need to be shipped for calibration unnecessarily.
With the synchronized voltage output, the transfer characteristics of the charge measurement chain can be identified easily.
Functioning and well calibrated measurement chains are the basis for failure-free operation of test benches, engines and industrial plants. The IfTA ChargeSignalGenerator ensures this from the beginning and helps to eliminate causes quickly in case of errors.
testing piezo-Based measurement chains Efficiently
Some measurement applications with piezo-based transducers require the use of external charge amplifiers, usually due to adverse environmental conditions. Such measurement chains are complex and hence prone to errors. The therefore required support for the setup and troubleshooting is provided by a portable sensor simulator.
The figure on the right shows a measurement chain with external charge amplifier. A measurement variable (M) generates a charge signal (Q) in the piezo-based transducer, which is transformed into a low impedance voltage signal (U) by the charge amplifier. Subsequently, this voltage signal is converted into a digital signal by an analog-to-digital converter (A/D). The sensor simulator - in the following denoted as charge signal generator (CSG) - is connected to the measurement chain instead of the sensor. This results in four important application scenarios.
Scenario 1: Calibration
The overall goal is to check the calibration of the entire measurement chain (without the sensor). In general, the process of calibration aims to achieve the best possible accordance between measurement variable and measured value. Therefore, the charge signal generator is used to feed a signal of defined amplitude and frequency into the measurement chain. The amplitude is selected in a way that it corresponds to a typical value of the measurement variable, e.g. 1.0 g for an accelerometer. At the other end of the measurement chain - represented here by a laptop - likewise an amplitude of 1.0 g as well as the frequency set at the charge signal generator should be displayed. If this is ensured for a number of typical input signals, the measurement result obtained in real operation can later be assumed to be plausible. For this application it is important to use a calibrated charge signal generator.
Scenario 2: Signal path tracing and troubleshooting
The goal here is to check the individual signal paths. This is done either to detect an existing error or to check the measurement chain before the first commissioning or after a modification. For this purpose, the CSG is connected at different points within the measurement chain. For the parts of the measurement chain - from the sensor point of view - after the charge amplifier, a voltage output instead of a charge output must be used. Appropriate devices therefore provide both output signals. For each installation point, it is evaluated how the signal at the measurement device changes: Does it become weaker? Do disturbances occur? Since the analysis is comparative, the CSG does not necessarily have to be calibrated. If you start the analysis at the sensor and then move towards the measurement device, this is called a forward analysis. If you proceed the other way round, this is called backward analysis. In this way, incorrect or bad wiring or faulty components can be systematically found and their influence on the measurement result evaluated.
Scenario 3: Checking Polarity
For certain applications the polarity of the sensor signal is of great importance, e.g. for modal analyses. The correct polarity can be determined efficiently by inserting an asymmetric signal, for example a signal that contains only the positive peaks of a sine wave. If, as shown in the figure, the positive "bumps" of the signal are displayed the wrong way round in the measurement system, there must be an incorrect wiring at some point in the measurement chain. This location can subsequently be narrowed down as described in scenario 2.
Scenario 4: Determining the TRANSFER FUNCTION
In general, the transmission characteristics of a measurement chain are frequency-dependent. This means that a harmonic input signal is - depending on its frequency - amplified/damped or phase-shifted to different degrees along the measurement chain. The detailed behavior is quantified by the transfer function of the chain, representing the amplification/damping (gain) and the phase shift (phase) of the output signal relative to the input as a function of frequency. In order to evaluate this function for specific frequencies, a harmonic charge signal (Q) with defined frequency is fed into the measurement chain. Parallel to this, a voltage signal of the same frequency and synchronous to the Q signal is fed past the measurement chain, directly into the measurement device. This voltage signal represents the reference unaffected by the measurement chain. From both signals the value of the transfer function for the present frequency can then be calculated. If this is repeated for several frequencies, it is possible to get an impression of the frequency-dependent response characteristics of the measurement chain.
Charge Signal Generator for Quality Management
option: Traceable calibration according DIN ISO 17025
With the market introduction of a traceable calibration of the IfTA charge signal generator to a national standard according to DIN ISO 17025, it can now also be used for quality management processes. The IfTA ChargeSignalGenerator thus enables highest precision for mobile testing and calibration of measurement chains in a handy format.
IfTA ChargeSignalGenerator CSG and CSG10
TWO VARIANTS - depending on the requested maximum amplitude
IfTA offers two versions of the IfTA charge and signal generator that differ in the maximum amplitude and the amplitude step size:
- IfTA ChargeSignalGenerator CSG for amplitudes up to 1.000 pC in 0.1 pC steps
- IfTA ChargeSignalGenerator CSG10 for amplitudes up to 10.000 pC in 1.0 pC steps
|Power supply:||4 x AA battery|
|Dimensions:||33 x 150 x 107 (H x W x L in mm)|
|Weight:||271 g (without batteries)|
|Differential charge:||LEMO OS.302|
|Charge single-ended:||BNC (female)|
Signal ouput for charge signal generator CSG
|Frequency:||1 ... 20.000 Hz in 0.1 Hz Schritten|
|Charge:||0 ... 1000 pC in 0.1 pC Schritten|
|Voltage:||0 ... 1000 min 0.1 mV Schritten|
|Wave form:||Sine and half sine wave|
Signal ouput for charge signal generator CSG10
|Frequency:||1 ... 20.000 Hz in 0.1 Hz step size|
|Charge:||0 ... 10000 pC in 1.0 pC step size|
|Voltage:||0 ... 1000 min 0.1 mV step size|
|Wave form:||Sine and half sine wave|
The charge and signal generator is supplied in a practical carrying case including a microdot adapter (BNC - 10-32 UNF).
The following adapters and adapter cables are optionally available:
- Lemo 0S.302 - 7/16-27 UNS-2A
- Lemo 0S.302 - wire end ferrules
- BNC - M4 x 0.35
The signal and charge generator is delivered with a factory calibration as standard.
The traceability of the factory calibration to a national standard (DIN EN ISO/IEC 17025) is optionally available.
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