Customizing Experiments Using the I/O Capabilities

Caution: Floating operation of your potentiostat can be compromised by improper connection to the Misc. I/O connector.

b.Collect Cyclic Voltammetry

c.Initialize Spectroscopy measurement

d.Wait for “spectroscopy” to finish.  

A “Delay” function was used in our example, but the Sequence Wizard could also be set to “listen” from the spectrometer when the measurement is completed using a “Digital Signal In” channel.

e. Set digital channel to Off (Low)
f. Increase rotation speed by 1000

A multimeter was used to confirm the signals coming from each channel of the Misc. I/O cable and the collected data can be seen on Table 1.

Table 1: Example data as collected by multimeter

Interface 5000/1010 Monitor Board Kit
The Monitor connector is a 9-pin DIN-type connector that plugs in the front of any Interface family instrument (Figure 2) and together with the Monitor Board Kit allows the user to monitor voltage or current during data acquisition. A detail of the pin-out signals of the Monitor connector are provided in Table C-2 on Appendix C on the manual:

- I Monitor Signal: Represent the output of the Interface instrument in the current measurements circuit (Filtered using an RLC circuit). Range is ±3V for the nominal full-scale current on the selected current range.
- E Monitor Signal: Is derived from the output of the Interface instrument differential electrometer circuit and therefore is the raw voltage signal with no offset or gain applied (Filtered using an RLC circuit).
- External Signal In: Allows to add a voltage to the Interface instrument signal generator. This signal is summed with the other signal-generator sources.
- Temperature Monitor Signal: Offers monitor in the range of –50 to 600°C. A 1000 Ω (at 0°C) platinum RTD (resistance temperature detector) according to European standard (DIN/IEC 60751 or simply IEC751) is used for the temperature measurement.
- AUX IN: Only available for the Interface 5000 family, allows the monitor board to measure a voltage outside the Interface 5000 using the internal A/D converter.

Example: How to properly monitor the voltage and current applied to the cell leads of an experiment without adding noise to the system.

Figure 2: Interface 5000/1010 Monitor Board Kit (#990-00401) and connector location.

Two experiments will be used.  In both, an oscilloscope will be used to 1) monitor the voltage (E) and current (I) applied to a LED light during a multi-step chronoamperometry scan and 2) monitor the current response of a 3F 2.7V Nesscap super-capacitor during a power cyclic voltammetry scan.

1) Multi-step chronoamperometry on LED light

A round 3V 5mm LED was connected to an Interface 5000E instrument as seen in Figure 3. The E Monitor Signal and I Monitor Signal were connected to channel 1 and 2 on a Tektronix TDS 3012 oscilloscope.

Figure 3: LED connections where W/WS are working and working sense electrode, C is counter electrode and R is reference electrode

Multi-Step Chronoamperometry was utilized to turn the LED light on, hold it for 3 seconds and turn it off for 1 second (sample rate of 0.01 seconds). The multi-step is an extension of Gamry Framework Chronoamperometry script and detailed description can be found in the Framework Help menu. The voltage steps and time duration can be seen in Figure 4.

Figure 4: Voltage Step detail on Multi-Step Chronoamperometry routine.

The data collected were analyzed using Echem Analyst software and plotted in a double Y-axis showing current and voltage dependance with respect to time as seen on Figure 5. A photograph of the oscilloscope main screen was captured during the test and can be seen on Figure 6.
The E monitor signal is a differential two wired buffered representation of the voltage difference between the white (Reference) and blue (Working sense) cell cables leads with the negative side connected to the Interface 5000 signal ground. The I Monitor signal is also a two wire differential signal with the negative side connected to the signal ground and is a representation of the current traveling between the red (Counter) and green (Working) cell cable leads.

Figure 5: Current and Voltage vs. Time using Echem Analyst software.  Bottom image is a zoom-in view of the first two pulses.

Figure 6: Picture of oscilloscope screen while performing Multi-Step Chronoamperometry

Note: Notice the faster sample rate on the oscilloscope (1.25Gsamples/second) showing the smooth current transients during charge/discharge compared to slower 100 sample/sec rate of the potentiostat.

2) Power cyclic voltammetry on super-capacitor
A similar set up as in Figure 3 was used, in which the LED light was replaced for a Nesscap 3F 2.7V super-capacitor. The capacitor was initially set in a state of low charge. The voltage of the super-capacitor was cycle from 1V→2.7V→0V twice using the Power Cyclic Voltammetry script (see Framework software help for details). The I/E range mode was set to Auto and the expected Max Current was set to 500mA. For more information on how to set up range mode on Gamry potentiostat please read “Current Ranges – Fixed vs. Autoranging” from our website https://www.gamry.com/support/technical-support/frequently-asked-questions/fixed-vs-autoranging. The current signal was monitored using the oscilloscope in a similar way as before while the voltage was not monitored in this instance. The data collected can be seen in Figure 7.
The low initial charge of the super-capacitor combined with a sudden ramping of voltage to 1V requires the instrument to provide a large amount of current (higher than the 500mA anticipated). The subsequent cycle (red line in Figure 7) stayed within ±500mA as expected. In this example, as the Cyclic Voltammetry experiment was set to auto-range the current, the instrument had to transition current ranges from a IE-Range #12 with a max current of 5A to a IE-Range #11 with a max current of 500mA. This transition can be seen in the blue line cluster in Figure 7.
When performing an experiment such as this one, it is better to choose to run the potentiostat on a fixed current range. Auto current range was chosen to show how the voltage representing current resets when the current range changes.  

Figure 7: Cyclic voltammetry data superimposed with monitor of current signal.

The scaling on the I Monitor Signal is ±3V for the nominal full-scale current on the selected current range. When the software is auto-ranging the current, the monitor signal will show as a discontinuous jump at each range change as it can be seen in the oscilloscope photograph (yellow curve) on Figure 7.

Conclusions
Gamry Instruments provides the user with several input and output options. In this note, we showed of how the User I/O connector allows for digital outputs for controlling external devices like a spectrometer. This connector also provides an analog voltage out, allowing control of external devices such as a rotating electrode. Also, by means of the Monitor connector together with the Monitor Board Kit, we showed that users could monitor currents and voltages response applied at the cell leads without inducing noise into the measurements. These capabilities are also available on the Reference family of instruments however, no Monitor Board kit is needed as the I Monitor and E Monitor are available on the rear of the instruments.

Gamry customers interested in custom application of the Auxiliary Input and Output capabilities should get in touch with Gamry.