5B34 Isolated, Linearized RTD Input


Model 5B34-01The 5B34 is a single-channel signal conditioning module that amplifies,protects, filters, linearizes and isolates a wide variety of two- and three-wire RTDs. For true four-wire RTD measurements please refer to the 5B35 section.

The 5B34 protects the computer side from damage due to field-side overvoltage faults. The module withstands 240 V rms at the input terminals without damage thereby shielding the internal computer-side circuitry from field-side overvoltage conditions. In addition, the 5B34 is mix-and-match and hot swappable with all other 5B Series input modules, so can be inserted or removed from any socket in the same backplane without disrupting system power.

Inside the 5B32 Series Module

Two identical sources provide excitation current for the RTD. For three-wire RTDs, the second current flows through the third RTD lead so as to cancel the effects of (equal) lead resistance; this current also flows through a stable resistor laser-trimmed to the RTD value that sets the differential amplifier input and (module) output to zero volts at that scale point. The current sources and the amplifier input are protected to withstand input overvoltage up to 240 V rms.

A differential chopper-stabilized input amplifier provides stable gain and exceptionally low drift. This allows the use of very low RTD excitation current to minimize self-heating and preserve measurement accuracy. Along with module gain and zero settings, a feedback linearizer is laser-trimmed. Custom versions of 5B34 can be laser-trimmed to meet special requirements.

Internal multi-pole lowpass filtering with a four-Hz cutoff (-3dB)enhances normal-mode (noise on signal) and common-mode (noise on signal return) rejection at 50/60 Hz, enabling accurate measurement of small signals in high electrical noise.

Signal isolation by transformer coupling uses a proprietary modulation technique for linear, stable and reliable performance. The differential input circuit on the field side is fully floating, eliminating the need for any input grounding. A demodulator on the computer side of the signal transformer recovers the original signal, which is then filtered and buffered to provide a low-noise, low-impedance output signal. The output common must be kept within ±3 V of power common.

Convenience Features

A series output switch eliminates the need for external multiplexing in many applications. The switch is turned on by an active-low enable input. If the switch is to be on at all times, the enable-input should be grounded to power common as it is on the 5B01 and 5B08 backplanes.

Input and Output Ranges

5B34 Functional Block Diagram

Figure 1. 5B34 Functional Block Diagram

5B34 Input Field Connections

Figure 2. 5B34 Input Field Connections

Input Ranges
Output Ranges
100 Ω Platinum RTD
0 to +5 V
10 Ω Copper RTD

120 Ω Nickel RTD

5B34 Models Available

Model  Input
Order Now 5B34-01
Platinum, α = 0.00385*
-100°C to +100°C (-148°F to +212°F)
0 V to +5 V  ±0.32°C
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0°C to +100°C (+32°F to 212°F)
0 V to +5 V
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0°C to +200°C (+32°F to 392°F)
0 V to +5 V
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5B34-04 0°C to +600°C (+32°F to 1112°F)
0 V to +5 V
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10 Ω Copper, α = 0.004274
0°C to +120°C (10Ω @ 0°C) (+32°F to +248°F)
0 V to +5 V
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0°C to +120°C (10Ω @ 25°C) (+32°F to +248°F)
0 V to +5 V
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120 Ω Nickel, * = 0.00672
0°C to +300°C (+32°F to +572°F)
0 V to +5 V

5B34-Custom * *

* Custom Input/Output ranges are available including versions for the 100Ω Platinum RTD with α=0.003916.
Refer to configuration guide.

5B34 Specifications

Description  Model 5B34
Input Ranges
Standard Ranges
Refer to Model Table
Custom Ranges
-200°C to +850°C (100 Ω Platinum)
-80°C to +320°C (120 Ω Nickel)
-100°C to +260°C (10 Ω Copper)
Output Ranges (RL > 50 kΩ)
0 V to +5 V
Initial @ +25°C
±0.05% Span ±0.04 Ω* ±0.05 (Rz1)
Conformity Error3
±0.05% Span
Input Offset vs. Temperature
Output Offset vs. Temperature
±20 µV/°C
Gain vs. Temperature
±0.005% of Reading/°C
Input Bias Current
±3 nA
Input Resistor
Power On 5 MΩ
Power Off 40 kΩ
Overload 40 kΩ
Input, 0.1 Hz to 10 Hz Bandwidth
0.2 µV rms
Output, 100 kHz Bandwidth
200 µV rms
Bandwidth, -3 dB 4 Hz
Output Rise Time, 10% to 90% Span
200 ms
Common-Mode Voltage (CMV)3
Input-to-Output, Continuous
1500 V rms, maximum
Output-to-Power, Continuous4
±3 V, maximum
Transient ANSI/IEEE C37.90.1-1989
Common-Mode Rejection (CMR)
1 kΩ Source Imbalance, 50/60 Hz
160 dB
Normal Mode Rejection 50/60 Hz
60 dB
Sensor Excitation Current
100 Ω Pt, 120 Ω Ni 0.25 mA
10 Ω Cu
1.0 mA
Lead Resistance Effect
100 Ω Pt, 120 Ω Ni  ±0.02°C/Ω
10 Ω Cu
Input Protection
240 V rms, maximum
ANSI/IEEE C37.90.1-1989
Output Resistance
50 Ω
Voltage Output Protection
Continuous Short to Ground
Output Selection Time 6 µs @ Cload = 0 to 2,000 pF
Output Enable Control
Max Logic "0"  +1 V
Min Logic "1"
+2.5 V
Max Logic "1"
+36 V
Input Current "0"
0.4 mA
Power Supply Voltage
+5 V ±5%
Power Supply Current 30 mA
Power Supply Sensitivity, RTI
100 Ω Pt, 120 Ω Ni ±0.05°C/V
10 Ω Cu
Mechanical Dimensions
2.275" x 2.375" x 0.595"
(57.8 mm x 59.1 mm x 15.1 mm)
Temperature Range
   Rated Performance -25°C to +85°C
   Operating -40°C to +85°C
   Storage -40°C to +85°C
Relative Humidity
0 to 93% @ +40°C noncondensing
RFI Susceptibility
±0.5% Span error @ 400 MHz, 5 Watt, 3 ft

* ±0.025 Ω For Cu RTD's; ±0.1 Ω For Ni RTD's.
1 Rz is the value of the RTD resistance at the lowest point of the measurement range.
2 Includes the combined effects of repeatability, hysteresis, 
and conformity error. Loads heavier than 50 kΩ will degrade conformity and gain temperature coefficient.
3 For Pt RTD's only; other types may vary.
4 The output common must be kept within ±3 V of power common.

Specifications subject to change without notice.