Minco TT269 Operating Instructions

MINCO

TT269

3-wire Temperature Transmitter

Installation and Operating Instructions

Description

Model TT269 is a 3-wire temperature transmitter for RTD (resistance temperature detector)
thermometers. The TemptranTM converts the RTD's signal into a 0 to 1 mA current. The
current changes according to the range marked on the Temptran: 0 mA at the lowest
temperature of the range, rising to 1 mA at the top of the range.

Installation

Locate the Temptran near the RTD, in an area where the ambient temperature stays between ­40 and 85 °C (-40 and 185 °F). Mount with #8 machine screws using the two mounting holes
provided in the Temptran case.

Connect the Temptran as shown below, observing the +/- polarity of the power supply
connections. Maximum DC supply voltage = 35 VDC. The maximum load resistance for the 0
to 1 mA output is 1000 Ω. The RTD connections for the Temptran in the wiring diagram below
must be connected as shown or the transmitter will not function properly.

Wiring Diagram

7300 Commerce Lane, Minneapolis, MN 55432-3177 U.S.A.
Telephone: [phone] / FAX: [phone]

PRODUCTS, INC

.

Calibration

NOTE: Because the transmitter cannot output a negative current, the calibration of the zero
cannot be performed at 0 °C (0 mA). The zero calibration should be performed at 6 °C (.05 mA)
to ensure proper calibration of the transmitter. If the transmitter is calibrated at 0 °C, the output of
the transmitter may not be linear.

1. Select the desired temperature range by soldering the two designated pins together.
For 0 to 120 °C Solder jumper 1 to A
For 0 to 160 °C Solder jumper 2 to A
For 0 to 180 °C Solder jumper 3 to A

2. Connect a power supply of 24 VDC, a 1000Ω load resistor (decade box), and a digital

multimeter (4-½ digit minimum) as shown below. The load resistor should have an accuracy of
1000Ω +/- .1 Ω. If unsure of the decade box's accuracy, measure using the DMM. Other load
resistances can be used as long as the maximum of 1000Ω is not exceeded. The required
calibration voltage measured on the DMM is dependent on the value of Rload according to the
following formula: V(DMM) = Rload x Current (Ohm's Law)

3. Connect a resistance decade box with a resolution of at least .01 ohms to the input of the
transmitter. If unsure or concerned about the decade box's accuracy, measure the zero and span
resistance settings using a known-accurate ohmmeter and record decade box settings before
connecting decade box to the transmitter.

4. Set decade box resistance to simulate 6 °C (102.34 Ω).

5. Adjust ZERO potentiometer until the meter reads .05 volts (.05 volts x 1000 Ω = .05 mA).

6. Set decade box resistance to simulate the desired span temperature.

For 120 °C R = 146.061
For 160 °C R = 161.043
For 180 °C R = 168.478

Ω
Ω
Ω

7. Adjust SPAN potentiometer until the meter reads 1 volt (1 volt x 1000 Ω = 1 mA).

8. Repeat steps 4 - 7 until no further adjustment is necessary. The zero and span pots are non­interacting so further adjustment should be minimal.

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