Series 3700 System Switch/Multimeter User's Manual Section 5: Basic Digital Multimeter (DMM) OperationDocument Number: 3700S-900-01 Rev. A / August 2007 5-35NOTE 1. INPUT Sense HI is internally connector to INPUT HI. The connection allows properopen circuit voltage, even with Sense HI disconnected. With INPUT Sense HIdisconnected, and the other inputs properly connected, the measurement will read theVDUT and RLEADVOLTAGE drop.2. For dmm.drycircuit = dmm.ON and dmm.opendetector = dmm.ON, IOPENLEAD willbe disabled, but a print(dmm.opendetector) will still return 1.0.Temperature measurementsThe Series 3700 can measure temperature using various thermoelectric transducers including:thermocouples, thermistors, and 3 or 4-wire resistance temperature detectors (RTDs). Whendeciding which type to use, keep in mind that the thermocouple is the most versatile and usefulfor significant distances between the sensor and the instrument, the thermistor is the mostsensitive, the 4-wire RTD is the most stable, and the 3-wire RTD minimizes the number ofconductors per sensor (3).ThermocouplesFor thermocouples, temperature measurement range depends on which type of thermocouple isbeing used. Thermocouples that are supported include types J, K, N, T, E, R, S, and B.Type Range ResolutionJ -200°C to +760°C 0.001°CK -200°C to +1372°C 0.001°CN -200°C to +1300°C 0.001°CT -200°C to +400°C 0.001°CE -150°C to +1000°C 0.001°CR 0°C to +1768°C 0.1°CS 0°C to +1786°C 0.1°CB +350°C to +1820°C 0.1°CWhen two wires made up of dissimilar metals are joined together, a voltage is generated. Thegenerated voltage is a function of temperature. As temperature changes, the voltage changes.The thermocouple voltage equates to a temperature reading. This is the basic operationprinciple of the thermocouple.When you connect a thermocouple directly to the input of the Series 3700, at least one of thoseconnections will be a junction made up of two dissimilar metals. Hence, another voltage isintroduced and is algebraically added to the thermocouple voltage. The result will be anerroneous temperature measurement.To cancel the affects of the unwanted thermal voltage, the thermocouple circuit requires areference junction that is at a known temperature.
