Allen-Bradley 1794-VHSC Flex I/O High-Speed Counter Module
Configured for high-speed pulse counting and frequency processing in EtherNet-enabled control networks, the Allen-Bradley 1794-VHSC (1794-VHSC Very High Speed Counter Module) provides direct physical/electrical execution. This 2-channel intelligent interface conditions differential encoder or pulse signals up to 1 MHz and executes real-time output switching across Allen-Bradley Flex I/O platforms.
Hardware Specifications
| Parameter | Specification |
|---|---|
| Model | 1794-VHSC |
| Brand | Allen-Bradley |
| Origin | USA |
| Weight | 0.56 lbs (0.26 kg) |
| Dimensions | 3.7 x 3.7 x 2.7 in (94 x 94 x 69 mm) with base |
| Operating Temp | 0 to 55 deg C |
| Power Consumption | 5.0 W at 31.2 VDC max (Thermal: 17.1 BTU/hr) |
| Flexbus Current | 75 mA at 5 VDC |
| Input Channels | 2 counter channels (2 groups of 3 inputs) |
| Maximum Input Frequency | 1 MHz |
| Nominal External Power | 24 VDC (19.2-31.2 VDC range, 100 mA at 24 VDC) |
| Output Ratings | 2 isolated groups (0.5 A at 5 VDC, 1.0 A at 12-24 VDC) |
| Isolation Voltage | 50 V continuous isolation between 6 areas (850 VDC for 1 s) |
| Compatible Terminal Bases | 1794-TB3G, 1794-TB3GS (Keyswitch Position 1) |
Backplane Bus Communication Velocity & EtherNet/IP Networks
The 1794-VHSC module interface links directly to the Flexbus backplane, drawing 75 mA at 5 VDC while transmitting high-speed counter telemetry across deterministic EtherNet/IP adapter networks. Up to 1 MHz pulse frequencies are processed on-module, offloading high-velocity axis tracking from the main PLC processor. Basic galvanic insulation tested at 850 VDC for 1 second maintains 50 V continuous channel-to-backplane isolation, protecting counting logic against field noise and common-mode surge propagation.
Frequently Asked Questions
Q: What key-switch position must be selected on the terminal base for the 1794-VHSC?
A: The terminal base key-switch must be rotated to position 1 to properly seat and key the 1794-VHSC module.
Q: Which terminal base units are compatible with the 1794-VHSC counter module?
A: The module installs directly onto either the 1794-TB3G or 1794-TB3GS grounded screw/spring terminal base units.
Q: What is the maximum pulse input frequency supported by the 1794-VHSC channels?
A: The input channels support high-speed pulse and quadrature encoder signals at frequencies up to 1 MHz.
Field Installation Guidelines
- Set the keyswitch on the 1794-TB3G or 1794-TB3GS terminal base unit to position 1 before attempting insertion.
- Push the 1794-VHSC module firmly into the terminal base until the locking mechanism latches completely into the backplane connector.
- Wire encoder signals using shielded twisted-pair cables, terminating shields at the designated ground terminals on the base.
- Connect external 24 VDC field power (19.2 to 31.2 VDC operating window) to supply output driver circuits and field transmitter loops.
- Ensure cabinet ambient conditions maintain operating temperatures between 0 and 55 deg C with non-condensing humidity between 5% and 95%.
Allen-Bradley 1794-VHSC Flex I/O High-Speed Counter Module
Allen-Bradley 1794-VHSC Flex I/O High-Speed Counter Module
Configured for high-speed pulse counting and frequency processing in EtherNet-enabled control networks, the Allen-Bradley 1794-VHSC (1794-VHSC Very High Speed Counter Module) provides direct physical/electrical execution. This 2-channel intelligent interface conditions differential encoder or pulse signals up to 1 MHz and executes real-time output switching across Allen-Bradley Flex I/O platforms.
Hardware Specifications
| Parameter | Specification |
|---|---|
| Model | 1794-VHSC |
| Brand | Allen-Bradley |
| Origin | USA |
| Weight | 0.56 lbs (0.26 kg) |
| Dimensions | 3.7 x 3.7 x 2.7 in (94 x 94 x 69 mm) with base |
| Operating Temp | 0 to 55 deg C |
| Power Consumption | 5.0 W at 31.2 VDC max (Thermal: 17.1 BTU/hr) |
| Flexbus Current | 75 mA at 5 VDC |
| Input Channels | 2 counter channels (2 groups of 3 inputs) |
| Maximum Input Frequency | 1 MHz |
| Nominal External Power | 24 VDC (19.2-31.2 VDC range, 100 mA at 24 VDC) |
| Output Ratings | 2 isolated groups (0.5 A at 5 VDC, 1.0 A at 12-24 VDC) |
| Isolation Voltage | 50 V continuous isolation between 6 areas (850 VDC for 1 s) |
| Compatible Terminal Bases | 1794-TB3G, 1794-TB3GS (Keyswitch Position 1) |
Backplane Bus Communication Velocity & EtherNet/IP Networks
The 1794-VHSC module interface links directly to the Flexbus backplane, drawing 75 mA at 5 VDC while transmitting high-speed counter telemetry across deterministic EtherNet/IP adapter networks. Up to 1 MHz pulse frequencies are processed on-module, offloading high-velocity axis tracking from the main PLC processor. Basic galvanic insulation tested at 850 VDC for 1 second maintains 50 V continuous channel-to-backplane isolation, protecting counting logic against field noise and common-mode surge propagation.
Frequently Asked Questions
Q: What key-switch position must be selected on the terminal base for the 1794-VHSC?
A: The terminal base key-switch must be rotated to position 1 to properly seat and key the 1794-VHSC module.
Q: Which terminal base units are compatible with the 1794-VHSC counter module?
A: The module installs directly onto either the 1794-TB3G or 1794-TB3GS grounded screw/spring terminal base units.
Q: What is the maximum pulse input frequency supported by the 1794-VHSC channels?
A: The input channels support high-speed pulse and quadrature encoder signals at frequencies up to 1 MHz.
Field Installation Guidelines
- Set the keyswitch on the 1794-TB3G or 1794-TB3GS terminal base unit to position 1 before attempting insertion.
- Push the 1794-VHSC module firmly into the terminal base until the locking mechanism latches completely into the backplane connector.
- Wire encoder signals using shielded twisted-pair cables, terminating shields at the designated ground terminals on the base.
- Connect external 24 VDC field power (19.2 to 31.2 VDC operating window) to supply output driver circuits and field transmitter loops.
- Ensure cabinet ambient conditions maintain operating temperatures between 0 and 55 deg C with non-condensing humidity between 5% and 95%.
