5B35 ISOLATED, LINEARIZED 4-WIRE RTD INPUT




Functional Description

5B35-03 The 5B35 is a single-channel signal conditioning module that amplifies, filters, isolates and protects a wide variety of four-wire RTDs. The module provides a linearized, highly accurate output of 0 to +5V.

Accurate and Stable Performance
The four-wire configuration of the 5B35 supplies RTD excitation from a precision, protected current source: two RTD wires carry the excitation current and two wires serve as signal-input leads that measure the voltage across the RTD. Because no excitation current flows through the signal-input leads, the length or resistance of the leads creates little or no RTD measurement error. A low-drift chopper-stabilized differential amplifier allows use of very low excitation current to minimize error due to RTD self-heating. The amplifiers low input offset drift of ±0.01°C/°C and gain drift of ±30 ppm/°C assure accuracy over the full operating temperature range.

True Three-Port Isolation
The floating, differential input circuit on the field side eliminates the need for any input grounding. Signal and power isolation by transformer coupling uses a proprietary modulation technique for linear, stable and reliable performance. 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. True three-port isolation (Input-Output-Power) includes common-mode ratings of : 1500 V rms between input and output and input and power; 250 V rms between power and output - no return path is required between the power and signal output commons.

Filtering and Protection
An optimized five-pole Butterworth filter (with a 4-Hz bandwidth) provides 116 dB of normal-mode rejection (noise on signal) at 60 Hz and 108 dB at 50 Hz. Output noise is an exceptionally low 0.3 mV p-p in a 100 kHz bandwidth and 6 mV p-p in a 5 MHz bandwidth.

The 5B35 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 5B35 is mix-and-match and hot swappable with all other 5B Series modules, so can be inserted or removed from any socket in the same backplane without disrupting system power.

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 connected to output common.



5B35 FBD


Figure 1. 5B35 Functional Block Diagram

Input Types

100 Ω Platinum RTD

10 Ω Copper RTD

120 Ω Nickel RTD

Output Range

0 to +5 V

 
5B35 IFC
Figure 2. 5B35 Input Field Connections

5B35 Models Available
  Model Input Range Output Range Accuracy
Order Now5B35-01100 Ω Platinum, Ο=0.00385*
-100°C to +100°C (-148°F to +212°F)
0 V to +5 V±0.26°C
Order Now5B35-020°C to +100°C (+32°F to +212°F)0 V to +5 V±0.13°C
Order Now5B35-030°C to +200°C (+32°F to +392°F)0 V to +5 V±0.26°C
Order Now5B35-040°C to +600°C (+32°F to +1112°F)0 V to +5 V±0.78°C
Order Now5B35-05-100°C to +200°C (-148°F to +392°F)0 V to +5 V±0.60°C
Order Now5B35-C-0110 Ω Copper, α=0.004274
0°C to +120°C (10 Ω @ 0°C) (+32°F to +248°F)
0 V to +5 V±0.23°C
Order Now5B35-C-020°C to +120°C (10 Ω @ 25°C)(+32°F to +248°F)0 V to +5 V±0.23°C
Order Now5B35-N-01120 Ω Nickel, α=0.00672
0°C to +300°C (+32°F to +572°F)
0 V to +5 V±0.40°C
 5B35-Custom** 
 5B35-C-Custom** 
 5B35-N-Custom** 
* Custom Input/Output ranges are available including versions for the 100 Ω Platinum RTD with α=0.003916. Refer to configuration guide.


5B35 Specifications
(typical @ +25°C and Vs = +5 V dc)
Description Model 5B35
Input Ranges
Standard Ranges Refer to Model Table
Custom Ranges-200°C to +850°C (100 Ω Platinum, α = 0.00385)
-80°C to +320°C (120 Ω Nickel, α = 0.00672)
-100°C to +260°C (10 Ω Copper, α = 0.004274)
Output Range (RL > 50 kΩ)0 V to +5 V
Accuracy1
Initial @ +25°CRefer to Model Table
Conformity Error±0.05% Span
Input Offset vs. Temperature±0.01°C/°C
Output Offset vs. Temperature±20 µV/°C
Gain vs. Temperature±0.003% of Reading/°C
Input Resistance
Power On> 1000 MΩ
Power Off200 kΩ
Overload200 kΩ
Noise
Input, 0.1 Hz to 10 Hz Bandwidth0.2 µV rms
Output, 100 kHz Bandwidth100 µV rms (0.3 mV peak-peak)
Output, 1 MHz Bandwidth1.5 mV peak-peak
Output, 5 MHz Bandwidth6 mV peak-peak
Bandwidth, -3 dB4 Hz
Output Rise Time, 10% to 90% Span100 ms
Common-Mode Voltage (CMV)
Input-to-Output, Continuous1500 V rms, maximum
Input-to-Power, Continuous1500 V rms, maximum
Output-to-Power, Continuous2250 V rms, maximum
TransientANSI/IEEE C37.90.1-1989
Common Mode Rejection (CMR)
1 kΩ Source Imbalance, 50/60 Hz190 dB (180 dB, Model 5B35-04)
Normal Mode Rejection (NMR)116 dB @ 60 Hz; 108 dB @ 50 Hz
Sensor Excitation Current
100 Ω Pt, 120 Ω Ni0.25 mA
10 Ω Cu1.0 mA
Lead Resistance Effect
100 Ω Pt, 120 ΩNi±0.00001°C/Ω
10Ω Cu±0.0001°C/Ω
Input Protection
Continuous240 V rms, maximum
TransientANSI/IEEE C37.90.1-1989
Output Resistance25 Ω
Voltage Output ProtectionContinuous Short to Ground
Output Current Limit±9 mA
Output Selection Time6 µs to ±1 mV of Vout @ Cload = 0 to 2,000 pF
Output Enable Control2
Max Logic "0"+0.8 V
Min Logic "1"+2.4 V
Max Logic "1"+100 V
Input Current "0", "1"0.5 µA
Power Supply Voltage+5 V dc ±5%
Power Supply Current15 mA
Power Supply Sensitivity, RTI±0.2°C/% of Vs
Mechanical Dimensions2.275" x 2.375" x 0.595"
(57.8 mm x 59.1 mm x 15.1 mm)
Environmental
Temperature Range
   Rated Performance-40°C to +85°C
   Operating-40°C to +85°C
   Storage-40°C to +85°C
Relative Humidity0 to 93% @ +40°C noncondensing
RFI Susceptibility±0.5% Span error @ 400 MHz, 5 Watt, 3 ft

1Includes the combined effects of repeatability, hysteresis, and conformity error. Loads heavier than 50 kΩ will degrade conformity and gain temperature coefficient.
2The user's board layout must separate Power Common from Output Common. When the output switch is not used, connect the Enable Input to the Output Common. Output Common is connected to power common when the 5B35 is installed on a 5B Series backplane.
Specifications subject to change without notice.

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