6B21 Isolated, Field Configurable Analog Input
6B21 Isolated, Field Configurable Analog Input
The 6B21 is a single-channel signal-conditioning module which provides a digitally-controlled isolated current loop output to a resolution of 12 bits. The output range can be selected to either a 0 to 20 mA or 4 mA to 20 mA process current. It is electrically and mechanically compatible with the 6B Series input modules and backplanes. The 6B21 takes a command from the host computer and converts it into an isolated process current suitable for interfacing with valves and actuators. The 6B21 offers a normal mode output protection of 240 V rms as well as 1500 V rms CMV isolation. In addition the actual current flowing in the current loop is read back by an on-board isolated V/F (voltage-to-frequency) converter.
Software Configuration
The 6B21 can be software-configured for address, output range, baud rate, data format, checksum status, slew rate, and start-up value. All programmable parameters are stored in the nonvolatile memory of the module.
Inside the 6B21
An on-board microcontroller communicates with the host through an RS-485 port to exchange command and status information. An included EEPROM stores calibration constants as well as configuration information. The microcontroller also controls the output DAC through an optically-isolated serial interface. The D/A converter drives the current loop through a protective V/I (voltage-to-current) converter. The output monitor is a V/F converter whose frequency is proportional to the loop current. This variable signal frequency is fed back to the microcontroller through an optical isolator. The microcontroller then scales the frequency signal and returns the current read-back data to the host computer. A DC/DC converter generates 25 V DC from the +5 V DC power supply to power the current loop and output circuitry.
Figure 1. 6B21 Functional Block Diagram |
Figure 2. 6B21 Field Connection Diagram |
Output Ranges |
Communications |
0 to 20 mA 4 mA to 20 mA |
RS-485-Interface |
Slew Rate (Software Configurable) |
Immediate Change |
0.126 mA/second |
0.250 mA/second |
0.500 mA/second |
1mA/second |
2 mA/second |
4 mA/second |
8 mA/second |
16 mA/second |
32 mA/second |
64 mA/second |
128 mA/second |
Range Description (Software Configurable) |
Accuracy (Typical) |
Accuracy (Maximum) |
0 mA to 20 mA |
±0.02 % FSR |
±0.05 % FSR |
4 mA to 20 mA |
±0.02 % FSR |
±0.05 %FSR |
6B21 Specifications
(typical @ +25°C and Vs = +5 V dc)
Specifications subject to change without notice.
(typical @ +25°C and Vs = +5 V dc)
Description |
Model 6B21 |
Outputs, Software Selectable |
|
Current, Operating Ranges |
0 mA to 20 mA or 4 mA to 20 mA |
Current, Overrange |
+2 mA ±200 µA |
Load Resistance | 0 to 750 Ω |
Communications |
|
Protocol | RS-485 |
Baud Rates, Software Selectable |
300K, 600K, 1.2K, 2.4K. 9.6K, 19.2K |
Output Current | |
Initial Accuracy |
|
Output Offset |
±5 µA (±15 µA maximum) |
Span |
±0.02% Full Scale Range (±0.05%, max.) |
Accuracy vs. Temperature | |
Output Offset Current | ±1 µA/°C |
Gain | ±50 ppm/°C |
Resolution | ±0.02% Full Scale Range |
Nonlinearity | ±0.02% Full Scale Range |
Output Noise, 0.1 Hz to 100 Hz Bandwidth | 1 µA peak-to-peak |
Bandwidth, -3 dB | 3 Hz |
Conversion Rate |
100 samples/second |
Setting Time | 1 ms to ±0.1% Full Scale Range |
Output Slew Rate | |
Software Selectable (11 Binary Ranges) |
0.125 mA/sec to 128 mA/sec |
Common-Mode Voltage (CMV) | |
Output-to-Input and Power |
1500 V rms continuous |
Common-Mode Rejection (CMR) |
|
Output-to-Input and Power @60 Hz |
108 dB |
Output Protection | 240 V rms, continuous |
Ouput Transient Protection | ANSI/IEEE C37.90.1-1989 |
Output Readback | |
Initial Accuracy @ +25°C |
|
Output Offset Current |
±100 µA |
Span | ±0.5% Full Scale Range |
Accuracy vs.Temperature | |
Output Offset Current | ±5 µA/°C |
Gain | ±200 ppm/°C |
Resolution | ±0.5% Full Scale Range |
Nonlinearity | ±0.5% Full Scale Range |
Power Supply | |
Voltage, Operating | +5 V dc ±5% |
Voltage, maximum safe limit |
+6.5 V dc |
Current |
+250 mA |
Mechanical Dimensions | 2.3" x 3.1" x 0.79" (58.4 mm x 78.7 mm x 19.1 mm) |
Environmental | |
Temperature Range | |
Rated Performance |
-25°C to +85°C |
Operating |
-25°C to +85°C |
Storage |
-40°C to +85°C |
Relative Humidity | 0 to 95% @ +60°C noncondensing |
Specifications subject to change without notice.