There are two different analog input lines on LabPro. They are Vin low (0 to 5 V) and Vin (-10 to +10 V). Most of the time we use the 0 to 5 volt line. The only exceptions are:

– The voltage probe which comes with LabPro or CBL or CBL 2
– some microphones

The microphone situation is complex. Most microphones are actually wired so that both lines come into the LabPro. These include: MCA-CBL and MCA-BTA. The ULI microphones are only wired to use the 0 to 5 V line. MPLI microphones are only wired to use the -10 to +10 V line.

Most experiment files used in Logger Pro 2.1 are set up to use the 0 to 5 volt line. Therefore, they should work with all microphones except the MPLI Microphones. To use a MPLI microphone, you need to open the file, select sensor setup and change the probe from Microphone to Voltage Probe (-10 to +10 V). Also, you need to change the triggering level, if trigger level is used. Note that the triggering needs to be set at about 0.1 volts for using the MPLI microphone.

In Logger Pro 3.x, the situation is pretty much the same as with LP2. To use an MPLI microphone via a CBL-8MC adapter, you need to set the sensor up as a +/- 10 volt Voltage probe, and not as a microphone.