The 1771-VHSC is a high-speed counter module developed by Allen-Bradley/Rockwell Automation. The 1771-VHSC module has Eight (8) digital outputs isolated in Two (2) groups, Twelve (12) digital inputs (3 per counter) and a 100-microseconds module update period. The 1771-VHSC module comes with Four (4) input channels that may be configured in rate mode, encoder mode, counter mode, and the period/rate mode. It has a programmable count value of 0 to 999,999. This high-speed module is also delivered with 2 input types (differential and single-ended inputs), compatible for use with a 2-phase encoder mode (X1 and X4) with selectable input frequencies of 250 KHz and 500 KHz in the rate/period or rate/measurement mode. Maximum supported frequency is 1 MHz in the single-channel counter mode selected by the electromechanical switch. In addition, this I/O module also provides block transfer programming capabilities that perform interface signals and high-speed counting with any PLC. Besides, the 1771-VHSC PLC 5 module counts pulses from encoders such as Allen-Bradley Bulletin 845H, P, L, E, P and K, pulse generators and mechanical limit switches or proximity switches and it returns either a count or frequency rating in a binary or BCD format.

Moreover, the 1771-VHSC module also offers electrical supplemental specifications, including the input voltage ratings which are 5 Volts DC or 12 to 24 Volts DC (user-selectable). The input current ratings are typically 7 mA at 5 Volts DC and 7.0 to 15.0 mA at 12 to 24 Volts DC and the required minimum input current is 4 mA. On the other hand, the output off-state leakage current is 10 µA at 24 Volts DC maximum while the on-state voltage drop is 0.05 Ohms x the maximum current. The backplane current ratings of the module are 650 mA and the isolation voltage between the I/O and backplane is 1500 Volts, respectively. Furthermore, the power dissipation is 13 Watts maximum and 2 Watts minimum. The thermal dissipation of this device is 54.2 BTU per hour maximum and 6.8 BTU per hour minimum. Lastly, the module operates at a 32 to 140 degrees Fahrenheit operating temperature range. The storage temperature range at which the module can be stored is -40 to 185 degrees Fahrenheit with 5 to 95% relative humidity without condensation.

This module occupies a single slot of the 1771 Chassis and energized via supplied power in the backplane. This module requires a backplane current of 650 mA. This module support switching frequencies of 100Hz for contact bounce; user-selectable electromechanical switch; 250kHz in encoder modes in 2-channel quadrature; 500kHz in period/rate, rate/measurement and continuous/rate modes 1MHz in single channel counter modes.

Four counting applications, this module may be integrated with high-speed sensors that is used to measure specific counts of a product or item. In motion control applications, this module supports integration of encoders attached to motors or servo motors for monitoring position and implementing control. It may also be used for totalizer applications wherein pulse generating instruments or metering device such as flowmeters may be wired to the module’s inputs to allow the program process and provide the equivalent totalized flow of the product.

This module supports Block Transfer Read (BTR) and Block Transfer Write (BTW) instruction for transferring of module to an from the processor. The module’s keying requirement is between 24 and 26 or 28 and 30. It uses a field wiring arm with catalog number 1771-WN. When wiring signals to the module, recommended conductors are Belden 9182 or equivalent with Category 2 and maximum length of 250 feet or 76.2m.