Minco TT859 Operating Instructions

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TT859 TemptranTM

2-wire Temperature Transmitter for RTD Thermometers

Installation and Operating Instructions

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Description

Model TT859 is a 2-wire temperature transmitter for RTD (Resistance Temperature Detector)
thermometers. The TemptranTM converts the RTD's signal into a 4 to 20 mA DC current. The
current changes according to the range in which the Temptran is calibrated: 4 mA at the lowest
temperature of the range, rising to 20 mA at the top of the range. The leads that supply power
also carry the current signal. The TT859 is FIELD RANGEABLE; the Zero and Span are adjustable
over -10 to 60°F and 35 to 150°F respectively allowing for re-ranging by means of a simple
calibration process.

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Specifications

Sensing Element:

1000 ohm @ 0°C platinum RTD, 0.00375 ohm/ohm/°C TCR or

0.00385 ohm/ohm/°C TCR.

Output:

4 to 20 mA DC over specified range.

System Accuracy:

± 0.5°F (± 0.3°C) @ room temp or ± 0.8% of span operating @
24 VDC.

Transmitter Linearity:

± 0.1% of span.

Rangeability:

Zero: -10 to 60F (-23° to 15°C).
Span: 35 to 150F (19° to 83°C).

Housing:

2.75” W x 4.50” H x 1.56” D. Bone white plastic cover and

baseplate with anodized aluminum endplates. Suitable for
indoor use only.

Operating Environment:

-40° to 185°F (-40° to 85°C), non-condensing.

Storage Environment:

67° to 212°F (-55° to 100°C), non-condensing.

Ambient Temperature

Effects:

± 0.01% Span/°F (± 0.018% Span/°C).

Warm-up Drift:

± 0.1% of span max., assuming Vsupply = 24 VDC and Rloop =
250 ohms. Stable within 15 minutes.

Supply Voltage:

9.4 to 35 volts DC, non-polarized.

Input Voltage Effect:

± 0.001% of span per volt from 9.4 to 35 VDC.

Maximum Load

Resistance:

The maximum allowable resistance of the signal-carrying loop,
including extension wires and load resistance, is given by this
formula: Rloop max = (Vsupply-9.4)/.02 amps. For example, if
the supply voltage is 24 VDC, the loop resistance must be less
than
730 .

System Integration:

Output “High” (22-25mA) with sensor open. Output “Low”
(3.3-3.7mA) with sensor shorted.

Zero and Span

Adjustment:

Non-interacting.

Maximum Output

Current:

28 mA.

Power Connections:

Screw terminals, non-polar (connect either way).

Sensor Connections:

Screw terminals, non-polar (connect either way).

Weight:

3.0 oz. (84 grams) Transmitter and housing.

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Installation

Installation of the TT859 consists of mounting the transmitter to a wall and connecting it to
power. The housing is mounted using two countersink screws to secure the base plate to a
wall. Access the mounting holes by separating the plastic base plate from the cover. Then
secure the base plate to the wall, long edge to the vertical (observing the directional arrow
marked on the base plate). Power and RTD wires are connected to the transmitter by 4 screw

terminals located near the edge of the circuit board (Figure 1). The transmitter’s power and

RTD connections are designed for non-polar hook-up, so polarity is not important. If
calibration is necessary, set dip-switches before assembling housing (See Transmitter Ranging
section).

Connect a DC source, not exceeding 35 VDC, to the “PWR” terminals as shown below (Figure

1).

Wiring Diagram

Figure 1

Power Supply

DC power supply requirements are determined by the TT859’s minimum voltage requirement
and voltage drop across the load resistor and installation lead wires.

Example: The transmitter requires 9.4 Volts minimum. A typical 250 ohm load resistor drops 5.0
Volts @ 20 mA. Allowing a margin of 0.5 Volts for the supply permits 25 ohms of lead wire
resistance for remote installation. Totaling these, we get a minimum power supply requirement
of 14.9 VDC.

Using a 24 VDC power supply will take care of nearly all installations, but the TT859 will operate
at voltages up to 35 VDC.