Vernier Software and Technology
Vernier Software & Technology
Tech Info Library

Can I use Vernier BTA sensors with a different A-to-D converter?

Vernier analog (BTA) sensors are usually used with Vernier interfaces. There are many interface options, see: http://www.vernier.com/products/interfaces/

In these cases, you just plug in the sensor and use our software. The sensor is automatically calibrated, and you start collecting data. If you want to write your own software but use Vernier analog sensors, the easiest way to do this is to use a Vernier interface and to start with the sample code at http://www.vernier.com/downloads/software-development-kits/ . This is made especially easy if you use LabVIEW.

If you want to use a Vernier sensor with a different analog-to-digital converter, you can probably get it to work, but it will be more work and there are several things you will need to consider.

- Making the connection: Vernier analog sensors use BTA connectors. The pinout can be found at http://www.vernier.com/probes/specs/pinout.html. Our product, Analog Protoboard Adapter, order code BTA-ELV, $10 , may help you make the connections. An advantage to using this device is that it has the 15k resistor built in that is used to complete the voltage divider circuit that is used on the Stainless Steel Temperature Probe, order code TMP-BTA, $29 and Surface Temperature Sensor, order code STS-BTA, $23 sensors.

Note that there is a 0 to 5 volt output for all of Vernier analog sensors, except for two:
-Voltage Probe, order code VP-BTA, $12, which is not really a sensor at all (it is just connecting wires). The -10 to +10 volt line is not connected to anything, in general.
-30-Volt Voltage Probe, order code 30V-BTA, $49, which basically divides the -30 to +30 volt input into a -10 to +10 volt output.

- Supplying power: All our sensors require +5.0 volt power supply. The ground line also needs to be connected.

- Calibration: Most Vernier sensors are linear in calibration (voltage vs. signal), so calibration is fairly easy. The calibration slope and intercept used are usually in the user manual that comes with the sensor or can be downloaded from the Vernier website.

Sensors that do not have a linear calibration include the following:
-Temperature probes TMP-BTA and STS-BTA: These are thermistors that are put into a voltage divider circuit that read the voltage at the midpoint. The voltage is related to the temperature by the Steinhart-Hart equation.
-Ion-selective electrodes have complex calibration curves.
-Our Wide-Range Temperature Probe, order code WRT-BTA, $82, Ethanol Sensor, order code ETH-BTA, $119, and Sound Level Sensor, order code SLS-BTA, $69 have quadratic calibration curves.
-Our Melt Station, order code MLT-BTA, $509 has a power equation calibration curve.
As mentioned above, the slopes and intercepts for standard calibrations are provided in many of the user manuals. These slopes and intercepts can only be used if the following are true:
-The input resistance of your interface is high.
-The power supply voltage you provide to the sensor is at 5.00 volts and well-regulated.

In general, you probably should do a calibration by taking voltage readings under different conditions.

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