Honeywell 900B08-0202 Analog Outputs 0 to 20mA, 8 Channel
Product Introduction
The Honeywell 900B08-0202 provides eight independent analog outputs. Each output scales from 0 to 21.0 mA per user settings. Outputs are isolated in two groups of four channels. Additionally, the module includes a failsafe feature for communication loss events. A slew rate function block limits output change speed when needed.
Technical Specifications
This I/O module operates with high precision. Its key parameters are listed below.
Outputs per module: 8, isolated as 2 groups of 4 (channels 1-4, 5-8)
Current range: 0 to 21.0 mA (user selectable)
Load resistance: 750 ohms max (highlighted)
Galvanic isolation: 500 VDC group to group, and from logic (highlighted)
Accuracy: 0.1% full scale at reference conditions
D/A resolution: 13+ bits (1 part in 13332)
Minimum current sensing: More than 0.5 mA per output
Modules per rack: 5 max (internal 24V backplane) / 10 max (external 24V backplane)
The Honeywell 900B08-0202 stores calibration data in non-volatile memory. It automatically rejects bad calibration versions. Moreover, it monitors factory calibration, configuration, and the +24 VDC power supply.
Diagnostics and Failsafe
A green blinking LED indicates the module is scanned. A red LED shows module or channel diagnostics. Users specify a failsafe value, such as hold last value or a preset mA level. This ensures predictable operation if communication breaks.
Output verification feedback tells the controller the actual output current. The slew rate function block converts a user’s rate limit into a maximum mA change per execution cycle.
Mechanical and Environmental Parameters
Terminal block required: Euro style 36-terminal (not included)
Isolation within group: None between outputs in same group
Update mode: Synchronous with control execution
Power source: Internal or external 24V backplane
Frequently Asked Questions (FAQ)
1. Can I mix 4-20mA and 0-20mA on the same module?
Yes. Each output on the Honeywell 900B08-0202 scales independently within the 0 to 21.0 mA range. You can set some channels to 4-20mA and others to 0-20mA.
2. What happens if the controller loses communication?
The module enters failsafe mode. You preconfigure either “hold last value” or a specific failsafe mA value per channel. This prevents unexpected process behavior.
3. Do I need an external power supply for 10 modules?
Yes. When you mount more than five modules per rack, you must use external 24V backplane power. The internal backplane supports only five modules max.
4. How do I verify the output current without an external meter?
The module provides output verification feedback to the controller. This internal reading confirms that current flows as commanded. However, for absolute accuracy, use an external meter.
5. Is the slew rate limit applied globally or per channel?
You apply the slew rate per channel using the function block. For instance, channel one can change at 1 mA/sec while channel five changes at 0.5 mA/sec. This allows flexible control.
