MeasPEx (Excitation Channels)

The MeasPEx argument specifies the number of sensors to excite with the same excitation channel before automatically advancing to the next excitation channel. To excite all sensors with the same excitation channel, the value of MeasPEx should be set equal to the Reps parameter.

If multiple sensors are measured during current excitation, the sensors should be connected in series, rather than in parallel. For example, instead of connecting the low side of the resistor to ground, the low side connects to the high side of the next resistor being measured. The last resistor in the chain will tie to ground. With the sensors connected in series, you need to consider the voltage that develops across each resistor when the excitation current is applied (V = IR). The sum of these voltages cannot exceed the specified compliance voltage for each excitation channel (+/- 5V). For example, if you’re exciting a string of 350-ohm resistors with the full 2.5 mA of current excitation, the voltage across each resistor is 0.0025 * 350 = 0.875 V per resistor. Then, 5 V compliance voltage/ 0.875 V per resistor = 5.714 resistors. So, you could measure up to five 350-ohm resistors per excitation channel. Hence, to measure eight of these sensors, 8 would be entered for the Reps argument and 5 for the MeasPEx argument. The first 5 sensors would all be connected to the first excitation channel, and the next 3 to the second excitation channel.