XPOT2
The XPOT2The BNC connector shields are connected to the test electrode (virtual ground) through a 2.2 kΩ resistor.he BNC connector shields are connected to the test electrode (virtual ground) through a 2.2 kΩ resistor.as a high precision auxiliary potentiostat adds an additional channel to the IM7 series potentiostat for bi-potentiostat functionality. The combination of IM7 and XPOT2 enables rotating ring disk electrode (RRDE) measurements or hydrogen permeation in Devanathan cells. The XPOT2 provides up to ±500 mA output current and up to ±25 V compliance voltage. The XPOT2 contains 9 current ranges which enable it to carry out outstandingly precise and accurate measurements.
In addition, the XPOT2 potentiostat can also be used as a standalone potentiostat and can be controlled by Zahner-Lab.
The Zahner’s potentiostats can be incorporated in a Python lab environment and can be used as stand-alone or in multi-channel configurations. A GitHub repository with examples is available for developing Python applications.
Standalone operation and possible integration in a Python work environment
Extension for bipotentiostat applications
Packing List
XPOT2
EPC42 cable
USB cable
Cell cable set:
4 BNC/banana cables (1 m)
4 banana clips
Power cord
Ring binder
Calibration report XPOT2
Risk assessment document
Zahner Analysis license keys
Product manual description
Caution
Caution
Prevent the inputs of the potentiostat from electrostatic discharge (ESD)! ESD may damage the potentiostat. ESD related damages are not covered in warranty of the potentiostat. The user must discharge his-/herself from any electrical charge before touching the potentiostat (TIP!: use grounded ESD-matts).
Please read the risk assessment document before operating the potentiostat.
Zahner’s potentiostats require a warm-up time of 30 minutes for optimum performance.
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.
To drive more than 32 A with the PP242 the customer must use a cable, recommended for high current applications and fix it to the front terminal CE and WE with suitable cable lugs.
Properly connect (with screws) the EPC42 cable with the electronic load. An accidental unplugging of the EPC42 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.
Introduction
Zahner’s power potentiostats XPOT2 can be used as an extension to the IM7 series potentiostats or in a stand-alone configuration. In the following sections, both scenarios are discussed.
Modular concept - extension to IM7 series potentiostat
The XPOT2 serves as an external auxiliary potentiostat, primarily designed for rotating ring-disk electrode (RRDE) experiments and multi-cell applications. When integrated with the IM7 series potentiostats, the XPOT2 becomes fully compatible and can perform all experimental techniques available to the IM7 systems. The XPOT2 delivers electrical currents up to ±500 mA with an output voltage range of up to ±10 V (compliance voltage: ±25 V). Connection between the XPOT2 and IM7 potentiostat is established using an EPC42 interface card.
The shields of the BNC connectors are connected to the test electrode (virtual ground) via a 2.2 kΩ resistor.
Caution
External power potentiostats connected to the IM7 series can only be operated sequentially. Simultaneous control of multiple power potentiostats is not supported.
Never connect or disconnect the D-SUB connector on the rear of the power potentiostat while either of the two devices is switched on. Failure to observe this precaution may result in damage to both the device and the test object.
Secure the D-SUB connector with the provided screws to prevent accidental disconnection.
When switching between devices, the non-selected external potentiostat will maintain its DC conditions, including DC potential or current and on/off status.
Voltage and current outputs of non-selected external potentiostats are neither measured nor monitored for compliance with defined voltage/current limits.
Only the currently selected external potentiostat is internally connected to the FRA (Frequency Response Analyzer) of the IM7 series potentiostat. Consequently, only the active external potentiostat can generate AC signals.
Stand-alone mode
Zahner’s power potentiostats or electronic loads (PP2X2, XPOT2, EL1002) can also be operated in stand-alone mode, for which a Windows 10/11 or Linux computer is necessary. For software updates, Windows 10/11 is required and the use of a virtual machine is not permitted. The application of a USB hub for connecting the device is not recommended.
The PP2X2/XPOT2/EL1002 potentiostat can also be controlled with other third-party software (e.g., Python). This allows for the integration in already established experimental setups. The potentiostats provide serial interfaces via the USB serial port which can be used to communicate with the potentiostat via the SCPI protocol. In the future, it is planned that the ethernet interface will be activated via a free software update.
Zahner has prepared a GitHub library for controlling the PP2X2/XPOT2/EL1002 potentiostats with Python via SCPI:
https://github.com/Zahner-elektrik/zahner_potentiostat
And a GitHub repository with examples using the library:
https://github.com/Zahner-elektrik/Zahner-Remote-Python
The API documentation can be found at:
https://doc.zahner.de/zahner_potentiostat
Only DC measurements can be carried out in the stand-alone mode.
Measuring Floating Objects
On the rear of the power potentiostats (PP2X2 and XPOT2), two connectors with a jumper are provided. If the jumper is set, the signal ground is connected to ground via a 100 Ω protective resistor. When examining grounded objects, the jumper on the back of the instrument must be removed. Otherwise, the device and the test object may get damaged.
Cell Connection Scheme
All Zahner potentiostats and power potentiostats follow the same cell connection scheme (4-electrodes connection scheme). The 4-electrode connection scheme includes connections for working electrode (WE), working electrode sense (WEs), reference electrode (RE), and counter electrode (CE). These connections are specified by their color code, WE: black, WES: blue, RE: green, and CE: red. To minimize interference, stray- and mutual inductance, the red and black power cables (current carrying cables) must be twisted together, and the green and blue sense cables must be twisted together before the measurement. Twisting is not shown in the schematic below.
Fig. 51 4-electrode connection scheme. The current is carried through the black (WE) and red (CE) wires. The voltage is measured between the green (RE) and blue (WEs) wires.
For large current flow the object must be connected with a four-electrode connection scheme in order to minimize the error margin in the measurement.
Contact Resistance
This figure shows a typical electrical wire used to connect the potentiostat with the test object. The resistance of the wire can be divided in to two parts (wire resistance and contact resistance).
Fig. 52 Typical electrical wire used to contact potentiostat with the test object. Resistance of the electrical wire is divided in to two different parts. 1) contact resistance and 2) wire resistance.
Two Electrode Cell Connection Scheme
Here a 2-electrode cell connection scheme is used for measurements on a cell. The WE and WEs cables are joined together to make one electrode connection and RE and CE cables are joined together to make the second electrode connection.
Fig. 53 The measured impedance (between RE and WEs electrodes) is the sum of the cell impedance and both contact impedances.
This means that the measured voltage is the sum of the object voltage and the two voltage drops across the contact resistances.
Four Electrode Cell Connection Scheme
The advantage of a 4-electrode connection scheme is illustrated here. With the WEs and RE being directly connected to the cell, the contact resistance for the WE and CE can be ignored as they don’t affect the voltage value (not possible with 2-electrode connection scheme).
Fig. 54 Four-electrode connection scheme and equivalent circuit diagram for a 2-electrode pouch cell.
For optimum measurement results, the WE and CE as well as the RE and WEs cables must be twisted together (not shown in the image).
Due to the high input impedance of the potentiostat the input current to the sense inputs is negligible. This means that there are no voltage drops across the contact resistances of the Sense connections. With the 4-electrode connection scheme, the contact resistances are in most cases not significant in the measured cell impedance. This is only true if the cell resistance of the test object is much smaller than the input resistance of the potentiostat. The input impedance of the potentiostat is provided in the specifications.
Specifications
Ranges and tolerances
Voltage Ranges |
|||||
|---|---|---|---|---|---|
Voltage Range Index |
Range Stand-Alone [V] |
Range IM7 [V] |
Tolerance |
||
min |
max |
min |
max |
||
0 |
-5.0 |
5.0 |
-4.0 |
4.0 |
±0.5 mV ±0.1% of reading |
1 |
-12.5 |
12.5 |
-10.0 |
10.0 |
±1.25 mV ±0.1% of reading |
Current Ranges |
|||||
|---|---|---|---|---|---|
Shunt Index |
Range Stand-Alone [A] |
Range IM7 [A] |
Tolerance |
||
min |
max |
min |
max |
||
0 |
-500m |
500m |
-500m |
500m |
±250 µA ±0.1% of reading |
1 |
-160m |
160m |
-160m |
160m |
±85 µA ±0.1% of reading |
2 |
-40m |
40m |
-40m |
40m |
±20 µA ±0.1% of reading |
3 |
-4m |
4m |
-4m |
4m |
±2.5 µA ±0.1% of reading |
4 |
-400µ |
400µ |
-400µ |
400µ |
±250 nA ±0.1% of reading |
5 |
-40µ |
40µ |
-40µ |
40µ |
±25 nA ±0.1% of reading |
6 |
-4µ |
4µ |
-4µ |
4µ |
±2.5 nA ±0.1% of reading |
7 |
-400n |
400n |
-400n |
400n |
±250 pA ±0.1% of reading |
General specifications
Potentiostatic Modes |
Potentiostatic, Galvanostatic, Pseudo-Galvanostatic, Off |
Cell Connection |
2-, 3-, 4-Terminal Sensing |
Ground Reference |
Grounded, Floating |
Compliance Voltage |
±25 V |
Maximum Current |
±0.5 A |
Output Power |
12 W |
Power Dissipation |
|
Input Impedance |
1 TΩ |
Equivalent Input Noise |
< 10 µV rms |
Memory |
64 GB |
Interface |
USB, Ethernet 2 |
Additional IOs |
5 2 |
Additional Analog Outputs |
1 2 |
Additional Analog Inputs |
4 2 |
Temperatur Sensor Interface |
Type K 2 |
Ambient Temperature |
10 °C - 25 °C |
Maximum Humidity |
60 % |
Dimensions (H x W x D) in mm |
160 x 185 x 327 |
Weight |
4.6 kg |
Zahner Lab / SCPI 3 |
|
ADC Resolution |
24 bits |
Voltage Input Resolution |
1.192 µV |
Current Input Resolution |
59.6 fA |
DAC Resolution |
18 bits |
Voltage Output Resolution |
76.3 µV |
Current Output Resolution |
3.81 pA |
IM7 3 |
|
ADC Resolution |
24 bits |
Voltage Input Resolution |
1.192 µV |
Current Input Resolution |
59.6 fA |
DAC Resolution |
16 bits |
Voltage Output Resolution |
250 µV |
Current Output Resolution |
12.5 pA |
Impedance Frequency Range |
100 mΩ - 1 GΩ |
Impedance Range |
1 µΩ - 1 kΩ1 |
Safe operating conditions
In this section, the safe operating range for the XPOT2 is provided. In the tables, the “power loss” is taken as an indicator of safe operating conditions. The XPOT2 potentiostat can accommodate a maximum power loss of up to 12 W. A higher power loss will trigger the safety precautions setup of the potentiostats and the output will be limited.
Caution
Please note that the “power loss” in the potentiostat is not the same as “power output” (=Current x Voltage).
Fig. 55 XPOT2 SOA