Figure 2
2. Determine sensor resistance corresponding to the lower and upper temperature range of the transmitter
from Tables 3 and 4 (page 6). Using “RTD Calc” a more complete resistance vs. temperature chart can be
printed; Download it from Minco’s web site, www.minco.com.
3. Set the decade box to the resistance value corresponding to the lower temperature. Adjust the Zero pot until
the milliammeter reads 4.0 mA +/- 0.016 mA.
4. Set the decade box to the resistance value corresponding to the upper temperature. Adjust the Span pot
until the milliammeter reads 20.0 mA +/- 0.016 mA.
5. Set the decade box to the resistance value corresponding to the lower temperature and verify that the
milliammeter still reads 4.0 mA +/- 0.016 mA. Correct if necessary, then repeat steps 4 and 5.
Transmitter Ranging
The transmitter is initially calibrated to a specific temperature range, as shown on the label attached to the
housing. Unless a different range is desired, ranging is not necessary. If the temperature range is changed,
recalibrate the transmitter as described in the section, Calibration Procedure.
When a different temperature range is desired, Tables 1 and 2 (Page 5) provide range switch settings
corresponding to the various temperature ranges. Switches 1 to 4 set the lower temperature limit (Zero) of the
transmitter. Switches 5 to 8 set the upper minus lower temperature (Span) of the transmitter.
For example, a temperature range of 50 to 200°F has a Zero of 50°F and a Span of 150°F (200-50). Table 1
shows the closest Zero range is 58°F with switches 1 through 4, respectively, in the ON, OFF, OFF, and ON
positions. Likewise, Table 2 shows the closest Span range is 155°F with switches 5 through 8, respectively, in the
ON, OFF, ON, and OFF positions. Once the switches are set, the Zero and Span trim pots should provide sufficient
adjustments to calibrate the transmitter.
In the event that the trim pots do not have sufficient adjustments, the switch settings should then be changed. In
the above example, if the Zero trim pot cannot adjust the transmitter current up to 4mA with the 58°F Zero switch
settings, then the Zero switch settings should then be changed to 38°F (ON, OFF, ON and OFF) which is the next
lower range. Likewise if the Span trim pot does not have sufficient adjustment, then the Span switch settings
should be changed.
