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Interfacing in Biology

Probes and Sensors

You may want to consider the following probes for the biology lab.

(Click here for suggested uses for these probes in biology)

Vernier Software makes other sensors and probes for use with the interfacing equipment. A brief description of all of the available probes can be found here.

What to purchase

This is not an easy answer, since different people do different things in the lab. I suggest purchasing sensors and probes necessary to do the labs you want to do. Make a list of the labs you want to perform or design. Examine books that have an assortment of labs already written. Select the labs you are most interested in and count the number of times a certain probe will be necessary. I find the temperature, pH, and pressure (Bio-Gas?) sensors extremely useful.

TI sensors and probes?

Several probes and sensors are designed exclusively for the CBL system, including a temperature probe, a light sensor, a microphone, and a motion sensor. These are automatically recognized by the CBL and do not require any adapter.

Note that almost all of the Vernier sensors and probes can be used with the CBL if you purchase a CBL-DIN adapter (very inexpensive). This adapter does not ship with the CBL (neither does an AC adapter). I would recommend having 3 or 4 CBL-DIN adapters per CBL unit.

You will need to write or obtain a program for the CBL system to perform most experiments.

Probe and Sensor List

Specifications, tips for use, and prices of several probes can be found below.


The pressure range is 24 to 32 inches of Hg (0.8 to 1.05 atm) absolute pressure. Do not get this probe wet! Water inside the box will ruin it. This sensor connects to a 3-way valve using plastic tubing.

Order Code BAR-DIN $56.00

Biology Gas Pressure Sensor

The Biology Gas Pressure Sensor is a new sensor that may replace the need for purchasing either a Pressure sensor or a Barometer. It combines the resolution of the barometer with the range most biology teachers require (0.7 - 1.5 atm). Do not get this probe wet! Water inside the box will ruin it. This sensor connects to a 3-way valve using plastic tubing.


This is a 3-color (red-635 nm, green-565 nm, blue-470 nm) colorimeter. It is great for determining the concentration of unknown solutions, or studying changes in concentration vs. time. Fifteen 3.5-mL cuvettes are included. (A package of 100 replacement cuvettes is available.

Order Code COL-DIN $99.00

Conductivity probe

This probe is great for environmental testing of water samples for salinity, total dissolved solids (TDS), or conductivity. Biology teachers can use this probe to demonstrate the migration of ions through membranes or to monitor changes in ion levels (such as HCO3-) in aquatic systems.

You can take readings in units of conductivity (S/cm) or concentration (mg/L and ppm as TDS or NaCl). The Conductivity Probe can monitor conductivity at three different sensitivity settings:

  • 0-100 mg/L TDS or 0-200 S
  • 0-1000 mg/L TDS or 0-2000 S
  • 0-5000 mg/L TDS or 0-10,000 S

Conductivity is directly proportional to concentration over the entire range.

The probe will reach 98% of full value in less than 10 seconds. A known standard (500 mg/L solution is provided for easy calibration. This probe is rugged and will not electrolyze solutions, as it uses alternating current.

Conductivity Probe (incl. probe, amplifier,500mg/L calibration solution). Order Code CON-DIN $79.00

Dissolved oxygen probe

Make fast, accurate measurements of dissolved oxygen in water samples using the Dissolved Oxygen Probe. This probe features:

  • Range: 0-20 mg/L (ppm) of dissolved oxygen.
  • Built-in temperature compensation, which means you can do your calibrations in the lab, and then make measurements outdoors without having to recalibrate.
  • Fast response time, reaching 95% of full reading in 30 seconds.
  • Pre-fit membranes. It's easy to change membranes on the dissolved oxygen probe. Disposable caps with pre-fit membranes allow one to quickly and conveniently change membranes. Two membrane caps are included.
  • Calibration: Simply place the electrode in the zero-oxygen solution provided with the probe for the 0% calibration point. For the 100% calibration point, place the electrode in air (or better yet, in water-saturated air, using a sealable bottle that is provided). You will need the barometric pressure and temperature of the room to look up the concentration of oxygen at saturation. The electrode can be calibrated in any units you choose: % D.O., mg/L, or ppm dissolved oxygen.

This probe requires a warm-up period of 30 minutes. If you use this with a CBL system, be sure to use an AC adapter during warm-up, or the unit may need new batteries in the field!

The DO-DIN includes the DO probe, amplification box, zero-oxygen solution, two membrane caps, a 100% calibration bottle, electrode filling solution, and a probe information booklet. Replacement caps are available.

Order Code DO-DIN $189.00; Replacement Membranes Order Code MEM $9.50

Heart rate monitor

A small ear clip is provided. An IBM, Macintosh, or Apple II Heart Rate Monitor Program is included if you are using this sensor with a computer. The Heart Rate Monitor Program displays a pattern representing your heart rhythm. It also displays the heart rate in beats/minute in large digits.

Order Code HRM-DIN $47.00

Light sensor

The Light Sensor approximates the human eye in spectral response and can be used over three different illumination ranges, selected with a switch. The ranges are 0-600, 0-6000, 0-150,000 lux.

Order Code LS-DIN $39.00

Magnetic field sensor

This sensor, which uses a Hall Effect transducer, is sensitive enough to measure the earth's magnetic field. Its two ranges are 3.2 gauss ( 3.2 x 10-4 tesla) and 64 gauss ( 6.4 x 10-3 tesla).

Order Code MG-DIN $44.00


Vernier Software manufactures two types of microphones. The microphone to get plugs into an interface and can be used for waveform and periodic function studies.

The ULI Microphone/Amplifier (MCA-U) is designed for the ULI interface. While this microphone may also be used with the MPLI or the CBL (using CBL-DIN adapter), there are other microphones designed specifically for these interfaces.

The MPLI Microphone/Amplifier (MCA-M) is designed for the PC's MPLI interface.. This microphone may be used with the CBL by using the CBL-8MC adapter.

The CBL Microphone/Amplifier (MCA-CBL) is a combination of the MCA-U and MCA-M. This was made to provide one microphone that could be used on either of the CBL input ranges (0 to 5V or -10 to +10V). This microphone plugs directly into the CBL without the need for an adapter.

Order Code MCA-U $30.00 (for use with ULI ); Order Code MCA-M $30.00 (for use with MPLI); Order Code MCA-CBL $30.00 (for use with CBL System)

Motion detectors

The Motion Detector is like the automatic range finder on a Polaroid camera. This is the same type of sensor that is also known as a "sonic ranger" or "ultrasonic motion detector". This sonar device emits ultrasonic pulses that reflect off objects in their path. The time it takes for the reflected pulses to return is used to calculate distance, velocity, and acceleration. The range of the sensor is 0.5 to 6.0 meters. We offer the same detector with different connectors for specific interfaces.

Order Code MD-CBL $64.00 (for use with CBL System); Order Code U-MD $65.00 (for use with ULI or CBL and CBL-RJ11 adapter); Order Code MD-M $66.00 (for use with MPLI or CBL and CBL-8MD adapter)

pH system

The pH System consists of a pH Electrode and pH Amplifier. The pH Electrode is an Ag-AgCl combination electrode with a range of 0 to 13 pH. The pH Amplifier contains the signal-conditioning circuitry. The pH Amplifier and pH Electrode are also available separately.

pH System - includes amplifier and electrode. Order Code PH-DIN $72.00; pH Amplifier only. Order Code PHA-DIN $40.00; pH Electrode only. Order Code 7120B $32.00; pH Buffer Capsules. Order Code PHB $10.00

Pressure sensor

The Pressure Sensor has a range of 0 to 100 psi (0 to 6.8 atm) absolute pressure. Do not get this probe wet! Water inside the box will ruin it. Plastic tubing connects to a 3-way valve. Older sensors have a metal valve, while newer sensors have a plastic valve. I prefer the plastic valves - they are sturdy and very easy to control.

Order Code PS-DIN $60.00

Radiation monitor

The Radiation Monitor consists of a Geiger-Mueller tube and rate meter mounted in a small, rugged, plastic case. The unit is battery operated and can be used without a computer for measurement of alpha, beta, and gamma radiation from background sources. It can be used with a ULI and the Event Counter software to explore radiation statistics, measure the rate of nuclear decay, and monitor radon daughters.

Compatible Interfaces: Universal Lab Interface (ULI)

Order Code U-RM $190.00

Relative humidity sensor

The Relative Humidity Sensor contains an integrated circuit that can be used to monitor relative humidity over the range 0 to 95% (+/- 5%). Unlike the barometer and pressure sensors, this sensor must be placed in the environment being measured. A plastic tube does not connect the sensor to the air.

Order Code RH-DIN $62.00

Temperature probes

Vernier Software manufactures a variety of temperature probes for use with various interfaces.

The Direct-Connect Temperature Probe is the low-cost way to measure temperature. The probe has a brass tube with a temperature sensor at the end. The tube is covered with Teflon heat-shrink tubing to make it resistant to chemicals. It plugs directly into any of the interfaces. The temperature range is -15 to +110 degrees C (+/- 0.2 degrees C in normal use). This probe cannot easily be used together with a DO probe, conductivity probe, or pH probe in the same solution, if the probes are attached to the same interface. To use it, wrap the probe in waran wrap to electrically insulate it from the water. It is, however, my preferred temperature probe.

The Standard Temperature Probe is a rugged, general-purpose laboratory temperature probe. The probe consists of a brass tube with a sensor at the end. The tube is covered with Teflon heat-shrink tubing to make it resistant to chemicals. The probe plugs into a small box which contains the signal-conditioning circuitry. The temperature range: -50 to +150 degrees C (0.2 degrees C in normal use). This probe can be used together with a DO probe, conductivity probe, or pH probe in the same solution, when the probes are attached to the same interface.

The Quick-Response Temperature Probe is electronically the same as the Standard Temperature Probe, but the sensor is in a smaller, ceramic package. The result is that the probe responds to changes in temperature much faster, but is less protected, both chemically and physically. Recommended for use in air and water only. The temperature range: -50 to +150 degrees C (+/- 0.2 degrees C in normal use).

The Thermocouple uses type-K thermocouple wire to measure the difference in temperature between its two junctions. It can be used over the range -200 to 1400 degrees C (+/- 10 degrees C). It is great for studying flame temperatures.

Direct Connect Temperature Probe DCT-DIN $25.00; Standard Temperature Probe TPA-DIN $43.00; Quick Response Temperature Probe TPAQ-DIN $49.00; Thermocouple TCA-DIN $35.00

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