FRA-Probe
The Zahner’s IM7 potentiostats have limited voltage and current ranges (i.e., IM7x: Voltage range ±15 V, Current range: ±4 A). Even with an extension of a Zahner’s electronic load (EL 1002), the maximum working voltage and sink current are 100 V and 200 A respectively.
In many applications, very high voltages or currents are needed. Here, a high power electronic device may carry out the simple DC measurements but AC measurements are usually not possible. For the AC measurements (i.e., EIS) the (external) high power device can be connected with the Zahner’s IM7 potentiostats via a frequency response analyser (FRA) probe. Besides the impedance measuring capabilities of the Zahner’s electrochemical potentiostats themselves, the potentiostats offer the feature to acquire the frequency response of an external device (EXD) by its FRA-Probe. The FRA-Probe is fully supported by the Zahner Lab software. Only the gain factors have to be set for each EXD individually.
Packing List
FRA-Probe set (E/I)
Connection cable to the IM7 potentiostats
Caution
Caution
Please read the risk assessment document before operating the potentiostat.
The FRA-Probe only outputs an analog setpoint signal for the external power device. The configuration and switching on/off of the external power device must be controlled separately by the user.
Do not connect active objects such as batteries or fuel cells to the power outputs of the potentiostat when the potentiostat is switched off! This may damage the potentiostat.
Properly connect (with screws) the E/I probe cables with the FRA-Probe. An accidental unplugging of the FRA cable during operation may damage your device.
Don’t touch the electrical connections during the operation.
The cables must be as short as possible and as thick as possible.
Requirement of the EXD
The EXD (external device) must provide an analog control input and analog signal outputs (current and voltage) so that it can be connected to the FRA probe. When an external device is used with the IM7/c/x potentiostat via a FRA-Probe then the IM7/c/x potentiostat works as a controller and the specifications of the potentiostat are irrelevant. Only the specifications of the EXD are relevant, hence the user must carefully select an EXD for the measurements. The user must pay attention to the “Rise Time” of the EXD. The Rise Time entails that how fast the EXD will apply the applied current/voltage.
The EXD specification range should be close to the desired current/voltage range of the system under investigation. An EXD with a very high current/voltage range will usually have a low resolution when it will be used for measurements at smaller current/voltage scales.
The EXD must be able to operate in the “constant current” (galvanostatic mode) and “constant voltage” (potentiostatic mode) settings. With this, the electrochemical impedance spectroscopy (EIS) measurements can be made in galvanostatic mode (constant current) or potentiostatic mode (constant voltage). For low ohmic objects, the constant current mode is mostly used.
The FRA can be configured to control a source, a sink, or a 4-quadrant electronic device.
The analog control input of the EXD should be in the range of ≤ ± 10 V.
The analog signal outputs of the EXD should be in the range of ≤ ± 10 V.
FRA - EXD Correlation
The internal potential ranges of all IM7 series potentiostats for the FRA application are ±4 V. The FRA-Probe is an interface that connects the IM7 series potentiostats to the EXD. The FRA-Probe works as an amplifier/divider that provides the output/input of the potentiostats to a widely used analogue interface value of ±10 V.
This ±10 V of the FRA-Probe must be correlated to the voltage/current range of the EXD via factors. In this way, the Zahner potentiostats can control the EXD. In the illustration below, the correlation factor (G) - for the voltage signal - between FRA and EXD is 20. If a voltage of +100 V is to be applied via the EXD, a voltage of +5 V is applied to the FRA interface.
Installation
The FRA-Probe consists of two interface boxes that are connected to the E probe and I probe connectors of the IM7 series potentiostat. Connect the FRA using the following steps:
Connect the E Probe cable of the FRA-Probe E to the E Probe input of the IM7/c/x.
Connect the I Probe cable of the FRA-Probe I to the I Probe input of the IM7/c/x.
Connect the Signal Out of the FRA-Probe I to the analog control input of the EXD.
Connect the Current In of the FRA-Probe I to the analog current output of the EXD.
Connect the Voltage In of the FRA-Probe E to the analog voltage output of the EXD.
Note
The external devices have different Analog I/O connectors, hence the user must custom-build a wire to connect the FRA-Probe to the Analog I/O of the EXD.
Offset Adjustment
The offset voltages of all three signals can be adjusted. For this a slotted screwdriver (size 0.4 x 2.5 mm) is needed. The potentiometer adjustment range is 10-13 turns, depending on the component used. The end stop can be detected by a soft click.
Specifications
Analog Control Output |
±10 V (DC + AC) ±5 V AC |
Current Monitor Input Range |
±10 V |
Voltage Monitor Input Range |
±10 V |
Frequency Response Range |
DC … 1MHz |
Inputs and Output |
differential in/out |
Gain Factors |
defined by software |
Note
The EXDs with higher specifications (high current/voltage range) will usually have longer rise times. Hence the user should not use an unnecessarily big EXD with the IM7/c/x potentiostat and FRA-Probe for the EIS measurements. Otherwise the usable bandwidth will be limited.