1-2. The Model 2180A Digital Thermometer is a portable, five digit RTD thermometer. Temperature measurements are possible, depending on RTD type employed, over a range of-219°C to +664°C (-394°F to + 1435°F) with 0.1° or .01° resolution. The instrument features: 1. Front Panel switch selection of Fahrenheit or Celsius readings. 2. Switch selectable RTD inputs. 3. Switch selectable input line voltage. 4. Dual slope measurement techniques. 5. Digital linearization of the RTD inputs. 1-3. DESCRIPTION I-4. The instrument display features seven, high- intensity, seven segment LEDs, and leading zero suppression. Six of the LEDs are used to display numeric data, with a minus sign for negative temperature readings. The remaining LED displays the selected temperature scale character (°F or °C). I-5. A four connection, screw-type terminal block is provided on the removable Input PCB for RTD connections. Input switch settings on this module will determine the microcomputer program necessary to linearize the desired RTD’s input. A precision, four-wire resistance measurement of the RTD is routed through this module to the thermometer’s input circuitry. 1-6. Selection of the temperature scale for display is made with a front panel pushbutton. The scale selected, Celsius or Fahrenheit, is displayed as the last character in the temperature reading (°C or ° F). A scale change can be made at any time, and has no effect on calibration of the instrument. 1-7. Options and accessories available for the 2180 A are listed in Table 1-1. More information concerning these items is given in Section 6 of this manual, Option and Accessory Information. 1-8. The measurement range of the 2180A Digital Thermometer is determined by the type of RTD used as the input device. RTD Types and total instrument accuracy specifications are listed in Table 1-2. Linearization of the RTD input is accomplished through toggling of the input switch segments on the RTD Input Module. Switch positions, numbers and applications are printed on the removable module beside the switch. 1-9. Four input line voltages are available for switch selection. Selection may be made for 100, 120, 220 or 240 volts ±10% as required to meet local conditions. Frequency may vary between 50 and 440 Hertz for all voltage selections. Refer to Section 4 of this manual when changing the selected input line voltage.