Model DI-5B35-03

Description

In RTD temperature measurement applications requiring a very high level of accuracy, the DI-5B35 4-Wire RTD input module offers a significant advantage over 3-wire measurement techniques (see block diagram). The DI-5B35 measures only the voltage dropped across the RTD and almost completely ignores the resistance or length of the RTD lead wires. The DI-5B34 3-Wire RTD module provides lead resistance compensation, but requires equal lead resistances, while the DI-5B35 does not require matched lead resistances.

Each DI-5B35 RTD input module provides a single channel of RTD input which is filtered, isolated, amplified, linearized, and converted to a high level analog voltage output. This voltage output is logic switch controlled, which allows these modules to share a common analog bus without the requirement of external multiplexers.

The DI-5B modules are designed with a completely isolated computer side circuit which can be floated to ±50V from Power Common, pin 16. This complete isolation means that no connection is required between I/O Common and Power Common for proper operation of the output switch. If desired, the output switch can be turned on continuously by simply connecting pin 22, the Read-Enable pin to I/O Common, pin 19. RTD excitation is provided from the module by a precision current source. The excitation current is available on two leads which are separate from the two input signal measuring leads. The excitation current does not flow in the input signal leads, which allows RTD measurement to be totally independent of lead resistance. The excitation current is very small (0.25mA for 100Ω Pt and 120Ω Ni, and 1.0mA for 10Ω Cu) which minimizes self-heating of the RTD.

Signal filtering is accomplished with a six-pole filter which provides 95dB of normal-mode-rejection at 60Hz and 90dB at 50Hz. Two poles of this filter are on the field side of the isolation barrier, and the other four are on the computer side. After the initial field-side filtering, the input signal is chopped by a proprietary chopper circuit. Isolation is provided by transformer coupling, again using a proprietary technique to suppress transmission of common mode spikes or surges. The module is powered from +5VDC, ±5%.

A special input circuit on the DI-5B35 modules provides protection against accidental connection of power-line voltages up to 240VAC.

Accessories

Specifications

Input Range:	0°C (32°F) to +200°C (+392°F)
Output Range:	0 to +5V
Accuracy:	±0.26°C (Includes conformity, hysteresis, and repeatability.)
Input Resistance:	Normal: 50MΩ Power Off: 40kΩ Overload: 40kΩ
Input Protection:	Continuous: 240Vrms max Transient: ANSI/IEEE C37.90.1-1989
Sensor Excitation Current:	0.25mA
Lead Resistance Effect:	±0.0005°C/Ω (“Ω” refers to the resistance in one lead.)
CMV, Input to Output:	Continuous: 1500Vrms max Transient: ANSI/IEEE C37.90.1-1989
CMR (50 or 60Hz):	160dB
NMR:	95dB at 60Hz, 90dB at 50Hz
Conformity Error:	±0.05% Span
Stability:	Input Offset: ±0.02°C/°C Output Offset: ±20µV/°C Gain: ±50ppm of reading/°C
Noise:	Input, 0.1 to 10Hz: 0.2µVrms Output, 100kHz: 200µVrms
Bandwidth, –3dB:	4Hz
Response Time, 90% Span:	0.2s
Output Range:	0V to +5V
Output Resistance:	50Ω
Output Protection:	Continuous Short to Ground
Output Selection Time (to ±1mV of VOUT):	6µs at Cload = 0 to 2000pF
Output Current Limit:	±14mA max
Output Enable Control:	Max Logic “0”: +0.8V Min Logic “1”: +2.4V Max Logic “1”: +36V Input Current, “0,1”: 0.5µA
Power Supply Voltage:	+5VDC ±5%
Power Supply Current:	30mA
Power Supply Sensitivity:	0.2°C/V
Environmental:	Operating Temperature: -40ºC to +85ºC Storage Temperature: -40ºC to +85ºC Relative Humidity: 0 to 95% Noncondensing RFI Susceptibility: ±0.5% Span Error at 400MHz, 5W, 3ft
Mechanical Dimensions:	2.28" × 2.26" × 0.60" (58mm × 57mm × 15mm)

* At standard 60Hz factory calibration. For 10 to 100% rated span. Add an additional 0.25% error for 0 to 10% Span measurements. Accuracy includes nonlinearity, hysteresis and repeatability but not source or external shunt inaccuracy (if used).

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