A Complete Measurement Solution...
The SIGNAL RECOVERY Model 9210 is a compact multichannel lock-in amplifier which uses the latest FPGA technology to deliver an instrument which can make complex AC and DC measurements on up to ten different analog signals. In addition it can generate excitation signals to drive the experiment, as well as measure the current delivered by these signals. It is therefore ideally suited to making direct impedance measurements on samples such as superconductors or in material analysis, as well as for use in optical, calorimetric, AC susceptibility, and many other experiments.
The unit is operated via a Gigabit Ethernet or USB interface from a free Windows compatible software package, or via a LabVIEW driver. Both packages allow full instrument setup and display of measured results in a wide range of digital and graphical formats.
This powerful instrument, in a slimline console which can stand on the benchtop or be rack mounted, makes the 9210 a valuable addition to any laboratory as well as a cost effective alternative to purchasing multiple instruments.
The Model 9210 can be ordered with between one and five dual channel signal processing modules. Each module includes a 20-bit DDS signal generator with 1.33 MSa/s update rate which is capable of outputting a sine, sawtooth, triangle, square, or noise waveform with or without a DC offset. The output frequency is selected from one of six programmable values or from one of two phase locked loops which will lock to external TTL logic signals, and the output amplitude is adjustable within three full scale ranges of ±10 V, ±1 V and ±0.1 V. The generator output can be taken directly as a single-ended voltage signal or as a floating signal with integrated output current measurement.
The signal generator output is coupled to the experiment. For example, in the case of a sample resistance measurement, it would be wired in series with the sample, while the voltage generated across it will then be connected to the model 9210’s signal inputs.
Each signal processing module includes two analog differential voltage input channels with twelve adjustable gain stages ranging from x1 to x5000, giving a full scale sensitivity range (pk-pk) of ±10 V to ±2 mV with a noise floor down to 1.8 nV/√Hz . Signals are then passed through anti-aliasing low pass filters before being sampled at 1 MSa/s by two 18-bit precision ADCs. A further ADC samples the signal representing the current being delivered by the generator.
The three digitized signals are then coupled to two sets of three parallel dual phase lock-in amplifiers per module. The reference channel inputs for all of these lock-ins can be the fundamental or harmonics of any of the frequencies being output by the signal generator(s). Each lock-in has output filters with selectable time constant and slope, and the resulting X, Y Magnitude and Phase readings are then available for display, storage or further processing.
Hence for a fully equipped system comprising five signal processing modules there are a total of 30 dual phase lock-in amplifiers. Each group of fifteen run at a common frequency, but the two groups can use different harmonics of the same frequency (Dual Harmonic Mode) or two unrelated frequencies (Dual Reference Mode). Because the instrument includes two phase locked loops the references can be either internally generated or from external frequency sources.
In addition to classic lock-in detection, the digitized signals can also be shown in a waveform plot (like an oscilloscope), or processed to give an FFT display. DC levels can also be measured and displayed synchronously.
Each module also includes a digital input which can be used to drive one of the two phase locked loops for external reference lock-in operation, and a digital output to use as a phase marker signal for the output from the signal generator.
Finally, a range of feedback options permit measured signals to affect the generator outputs on other channels, or to allow auto-levelling operation, where the generator level is continuously adjusted to give a constant input signal.
RJ45 connectors are used for the signal connections, since these provide a very compact way of terminating multiple connections using screened twisted pair cables. Cat-7 cables can be connected directly to the connectors, with the other end prepared for direct connection to the experiment. Alternatively, if the system is to be used with cryostats in which the signal connections will be made within the vacuum chamber, then Cat-7 jumpers can be connected from the 9210 to low-cost vacuum compatible multipin feedthroughs on the cryostat which allow vacuum integrity to be maintained.
Common applications of the Model 9210 multichannel measurement system include:
- Transport measurements, bridges
- Multi-terminal measurements
- Differential dI / dV characteristics
- Hall-probe arrays
- Calorimetry (AC steady state, 3-omega, relaxation)
- AC susceptibility
- Thermal conductivity
- Laser stabilization
- Optical spectroscopy, interferometry
- Strain-gauge systems
- Vibration measurements
- Semiconductor/photovoltaics characterization
- Correlation measurements