Minco
Tel: 763. 571.3121 • Fax: 763. 571.0927 • www.minco.com
5
Calibration Procedure
1.
Connect the equipment as shown below (Figure 2) substituting a resistance decade box,
with resolution of at least 0.01 ohm, in place of the RTD.
DECADE
BOX
SPAN ADJ.
ZERO ADJ.
4-20 mA
LOOP
mA
INDICATOR
24 VDC
POWER SUPPLY
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 30 to 90°F has a Zero of 30°F and a Span of 60°F (90-30).
Table 1 shows the closest Zero range is 30°F with switches 1 through 4, respectively, in the OFF,
ON, ON, and OFF positions. Likewise, Table 2 shows the closest Span range is 57°F with
switches 5 through 8, respectively, in the ON, ON, OFF, and OFF positions. Once the switches
