The ProboStat has feedthroughs for 6 electrode contacts and 4 shields, and can thus make the best out of any available impedance bridge, voltmeter and potentiostat/galvanostat. Here we comment on a few, for the benefit of those who have the instruments and are considering a ProboStat, or are buying a ProboStat and want to choose instrumentation for it.

Impedance spectrometers

Solartron Analytical (http://www.solartronanalytical.com), now part of Ametek, manufactures a range of impedance spectrometers, such as the 1260 FRA (Frequency Response Analyzer). The 1260 is well-proven with the ProboStat in our collaborating laboratory at the University of Oslo, and the shields bridge and ground switches of the ProboStat are designed to work with a 1260 and similar instruments. It offers a wide range of frequencies, oscillating voltages, DC bias, and processing controls. It can be used to measure highly conducting materials with 4 electrode geometries as well as highly insulating material with conductances down to the nS (resistance of Gohm) range.

Potentiostats like Solartron's 1286 or 1287 can be connected between the 1260 and the ProboStat, giving a higher input impedance and more possibilities in terms of DC experiments and biased AC spectroscopy. The practical upper frequency becomes limited to around 1 MHz by attaching a potentiostat.

The high impedance interface 1296 increases the measurable range to higher impedances nominally by several orders of magnitude.

Novocontrol Gmbh (http://www.novocontrol.de) produces impedance spectrometers of high quality. They cover a frequency range of 3 µHz - 20 MHz and have very high input impedances. They can thus be used as standalone instruments for dielectrics etc. A high input impedance sample interface that can do 2, 3, and 4-wire measurements is available, and this allows impedance ranges from 10 mOhm to 100 TOhm.

Other information: Economy models limited to 0.3 or 3 MHz available. Optional high voltage boosters for 300 or 1000 Vpp available. Software have drivers also for HP and other analysers and Eurotherm controllers.

We have tested a Novocontrol ALPHA analyzer with a four-terminal interface (for 2, 3, or 4 wires), and both the hard- and software do the job beautifully. It is fully compatible with the ProboStat in every respect. Especially the high impedance measurements are impressive.

Hewlett Packard / Agilent (http://www.agilent.com) produces a range of impedance spectrometers. The most versatile for work with a cell like the ProboStat is the good old HP 4192A. It is well-proven with the ProboStat, and the ProboStat's shields bridge and ground switches function well with the 4192. However, the lower frequency limit is as high as 5 Hz and the performance close to this limit is poor. This prevents most electrochemistry and also interpretation of spectra of very insulating materials (large time constants). The oscillating voltage, bias range and control of measurement quality by integration are all more limited than in e.g. the SI 1260 FRA and Novocontrol spectrometers.

Use it if you already have it. (Consider complementing the one you have with an affordable Gamry system (see below) for the low frequencies).

Gamry Instruments (http://www.gamry.com) produces potentiostats/galvanostats that sit on PC cards and readily fit into a desktop computer. These function also as impedance spectrometers with the right software package. The instruments are designed for electrochemistry, but they have all the functionality and specifications you may need for impedance studies of materials, too (4+ terminals, 2 reference electrodes, guard and ground terminals, etc). They go to very low frequencies, while the upper frequency is 300 kHz. This is because here the impedance spectrometer is bundled with the potentiostat, and this frequency is where any such combination from any brand starts to loose accuracy anyway.

The model to choose is a PCI4. If you work with fuel cells or batteries, need to do voltammetry or other DC work, or biased impedance spectroscopy, so that you need a potentiostat sooner or later, and if your budget is limited, the Gamry PCI4 system may definitely be your choice.

As mentioned, you cannot disconnect the potentiostat and therefore you cannot go to 1 MHz or a little more which you could if you had a separate impedance spectrometer, and which may be useful sometimes for investigation of bulk and grain boundaries in materials.

We have tested a PCI4/750 with a ProboStat and found it handled any measurement and any impedance. The contacts of the PCI4 are banana plugs that need to be connected to the ProboStat's BNC contacts using 4 standard banana-to-BNC adaptors (that we may supply).

Gamry's software is more oriented to electrochemistry than to materials, e.g. the recording plot (impedance or admittance parameters vs time) is rather coarse. However, an update is around the corner that maybe deals with this.

Conclusion: Good choice if your budget does not allow separate top-class spectrometer and potentiostat.

Ametek Princeton Applied Research (http://www.princetonappliedresearch.com) produces a range of well-known potentiostats as well as new models with integrated impedance spectroscopy, tested OK with the ProboStat.

Eco Chemie (http://www.autolab-instruments.com) designs and produces Autolab module based potentiostats/galvanostats (PGSTATS) for electrochemistry. The PGSTAT combined with FRA2 module for EIS measurements allows to perform both potentiostatic and galvanostatic impedance measurements over wide frequency range of 10 μHz to 1MHz. We have testet the instrument with the ProboStat and find that the combination works very well.

Others: Zahner, Hioki, Radiometer, etc. are instrumentation that will work well with the ProboStat.