Frequently Asked Questions isoPods

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You can learn more about the isoPods by looking at our range of isoPods, videos, and manuals.

Where can I find a driver for my eDAQ hardware?

The drivers are on the installation software thumb drives and CDs that are sent from eDAQ. When you install the software, the driver will be copied onto the computer.

The drivers are also found here and on the installation file when you download the software from the software download page

Have a look at this troubleshooting application note.

I have opened Pod-Vu software but the green Start button is grey and I cannot record any data.

Either:

  1. Pod-Vu software was started without the isoPod connected to the computer with the USB cable, or without a power cable. Close Pod-Vu software, connect the USB and power cables, and restart Pod-Vu software.
  2. The isoPod hasn’t been recognised by the computer or the driver hasn’t been installed. Have a look at this application note.
  3. If you are using the EPU452, it hasn’t been configured properly, for example, all channels have been turned off. Close Pod-Vu software, open MF Configurator software and configure the channels properly.

Do you happen to have any LabVIEW script for any of our USB-devices (EPU / ER815) which may be helpful to point a LabVIEW user in the right direction ?

Basically any eDAQ product which supports our serial protocol such as the isoPods, HV sequencer, Waveform generator etc can be controlled by NI LabVIEW - and other software like C++. LabVIEW has facilities to access and communicate via a virtual serial port such as used by edaq devices.

File:LabVIEW isoPod.zip is a simple example of a LabVIEW Vi that was written as an example - ( it is not proven). eDAQ can provide advice and support on its serial protocol but eDAQ does not provide NI instruments in support of its devices.

How can I use the isoPod if I have separate ion selective and reference electrodes?

QUESTION: I just bought EPU353 isoPod for pH/ISE from eDAQ. How could I use this isoPod for ISE if I have separate ion selective electrode and reference electrode? The isoPod has only 1 BNC plug connection. Where could I connect the reference electrode? Or do I need to make my new ISE with the build-in reference electrode, similar to a conventional pH electrode probe?

ANSWER: There is information about this at EPU353 and in the manual.

The manual says “Half cell electrodes require the use of a separate reference electrode which can be connected to the shell of the input BNC connector.” This means you need a T-piece . You connect the measuring ISE to the inner pin of the BNC, and the reference electrode to the outer shell of the BNC.

Some Questions about the EPU452 Quad Multi Function isoPod

QUESTIONS:

  1. If I use the EPU452 in the conductivity mode, how does it decide the amplitude and frequency of the applied sine wave for each range?
  2. If I use the EPU452 in the biosensor mode, what is the smallest stable voltage that I can apply? What is the step size of the voltage? Overall, how stable is the applied voltage?
  3. In the voltmeter mode, what is the accuracy and stability of the measurement?

ANSWERS:

  1. The ER452 uses a proprietary waveform technique which adapts its frequency and amplitude to the conductivity being measured. Maximum amplitude 200mVpp.
  2. Currently 1 mV was chosen as the smallest convenient increment of Poise voltage. The 16 Bit DAC that generates this voltage could produce increments of 0.1mV if required. The smallest voltage that can be applied is 0.0mV with an error of +/- 0.1mV typically 10uV. Stability is better than 10uV.
  3. Voltmeter mode: Accuracy 0.1% +/- 1mV. Stability is >10uV

Using the dissolved oxygen isoPod and the relationship between the measured signal and temperature

QUESTION: I prepared three PBS solutions at different temperatures. First, I immersed the electrode in 37 degrees solution and record a few minutes, then I transfer it to 25 degrees solution. Finally, I moved it to 15 degrees solution. Why did I observe that dO2 signal decreases as temperature decreases? I expected the opposite, because more dissolved oxygen is present in water with a lower temperature compared to water with a higher temperature (the reason for this inverse relationship between dissolved oxygen and temperature is that the solubility of a gas in a liquid is an equilibrium phenomenon).

ANSWER: Oxygen is more soluble in cold water than in hot water so the signal would tend to go down if the temperature increases. However, diffusion across the electrode membrane is faster at higher temperatures which tends to give a bigger signal. Thus, whether the signal actually rises or falls with temperature will depend on these two factors - which is hard to predict. This is why temperature should be maintained at a constant value! Trying to compare signals from samples with different temperatures is usually a futile exercise.

In flow electrodes, faster flow rates tend to give bigger signals. Eventually there will be a threshold flow rate above which the signal will remain constant. It is essential that calibration and subsequent measurements are done at the same constant flow rate.

Likewise, when using a 'dip in' electrode, the solution should be stirred at a constant rate.

NOTE ABOUT CALIBRATION:

  • Details for calibration of USB isoPods can be found in the Pod-Vu manual.
  • Calibration of the e-corder dissolved oxygen isoPod is usually done with Units Conversion feature in Chart software.
  • It is essential that calibration of the dO2 isoPod is done at the same temperature as subsequent measurements.
  • The signal should be proportional to the oxygen concentration (although there may be a small offset error, so that there is still some signal at zero oxygen concentration). This is why a two point calibration at zero and 100% saturation is usually necessary.