second. The displayunit associated with the measurement is shown in smaller
typeto the right of the measurement. The possible display units are degrees
Celsius (C), resistance in ohms (Ω), degrees Fahrenheit(F), Kelvin (K), and
degreesRankine (R). The display units can be easily changed accessing the
Units mode (see Section 7.6).
The lowerpart of the display has various functions depending on the selected
mode. It has smaller alphanumericcharacters. It can be used to display mini-
mum and maximum measurements, delta(x) measurements, or measurements
stored in memory.It is also used to view and set various operating parameters.
The modeis easily changed using the MODE button. (See details on the vari-
ous modes beginningwith Section 7.)
The displayhas a backlight that can be switched on for better viewing in dim
light.The backlight is switched on and off by pressing and holding the power
buttonfor three seconds (see Section 6.3 above). Note: The battery discharges
more quickly when the backlight is used.
6.5 Probe
The probe is used to sense temperature and attachesto the 1522 using aHart
INFO-CON probe connector thatplugs into the top of the instrument. The
probeconnector must be properly programmed with the correct charac-
teristics of the probefor measurements to be accurate (see Section 6.6).
The 1522 can be used withvarious types of PRT and thermistor probes:
•ITS-90 calibrated 25Ωor 100ΩPRT
•IEC-751 or DIN-43760 PRT (RTD)
•Callendar-VanDusen calibrated 100ΩPRT
•YSI-400 series or equivalent 2252Ωthermistor
•Steinhart-Hart thermistor polynomial; nominal R(25°C) 2kΩto 100kΩ
See Section 7.9.8 for detailson thevarious probe typesand theirprogramming.
The 1522 cannotbe used with thermocouples.
The 1522 can be used withprobes having two, three, or four wires. Three-wire
probes allowpartial compensation for wire resistance. The 1522 measures
three-wireprobes u sing thefollowing sequence. It measures the sensor resis-
tance, includingthe lead resistance in C2. The 1522 then directly measures the
resistance in the C1lead of the sensor and subtracts the measured C1 lead resis-
tancefrom themeasured sensor resistance (including the C2 lead resistance) to
obtain the sensor resistance used to calculate temperature. Note: This sequence
assumes thatthe lead resistance of C1 and C2 are equal. If C1 and C2 each
havea different resistance value, there will be an error in the calculated sensor
resistanceequal to this difference. Four-wire probes allow complete rejection of
wire resistance and should be used when the best accuracy is desired. The 1522
wire setting must be set to match the actual number of wires of the probe (see
Section 7.9.14).
1522 Handheld Thermometer Readout
User’s Guide
28