Vernier Software and Technology
Vernier Software & Technology
Tech Info Library

Can I use my third-party ISE with my Vernier equipment?

Maybe. The answer to this depends on a couple of things.

1. Does your electrode have a BNC connector? If so, you can use it with the Electrode Amplifier, order code EA-BTA, $40, the Go Wireless® Electrode Amplifier, order code GW-EA, or the Go Direct® Electrode Amplifier, order code GDX-EA, $64. The EA-BTA amplifier can be used with electrodes having an output of -450 mV to 1100 mV. The GW-EA and GDX-EA amplifiers can be used with electrodes having an output of -1000 mV to +1000 mV. Your third-party ISE voltage output must fall within this range.

2. Because the range of our amplifiers are so wide, your ISE may require only a very small part of this voltage range. Though you'll compromise, somewhat, when it comes to resolution, you can still get a fairly good reading.

To use a third-party ISE with an electrode amplifier, connect the ISE to the an electrode amplifier and connect it to a Vernier interface. Ensure the units are set to mV in the data-collection program. This setting will be remembered for subsequent uses of the sensor.

Change the data-collection mode to Events with Entry. Enter the name for the Event, i.e., Concentration (mg/L). A graph of Potential (mV) vs. Concentration will be graphed during data collection. The graph will be an exponential plot. To linearize it, create a new calculated column of ln Concentration and plot mV vs. ln Concentration. From there you can create a linear curve fit, then interpolate and determine the concentration of an unknown. To convert an interpolated ln Conc value back to the concentration you'll need to take the inverse ln.

Some common ISE voltage ranges (approximate):
Nitrate: 25 mV to 260 mV
Chloride: 0 mV to 240 mV
Calcium: -45 mV to 100 mV
Ammonium: -55 to 240 mV
dissolved CO2: -20 mV to 90 mV
Ammonia: -210 mV to 160 mV
Lead: -230 mV to -115 mV
Copper: 70 mV to 240 mV
Sodium: -80 mV to 260 mV
Fluoride: -100 mV to 200 mV
Bromide: -40 mV to 140 mV

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