{"product_id":"allen-bradley-hi-1756-2df-controllogix-pulse-frequency-input-module","title":"Allen-Bradley HI-1756-2DF ControlLogix Pulse Frequency Input Module","description":"\u003ch2\u003eAllen-Bradley HI-1756-2DF ControlLogix Pulse Frequency Input Module\u003c\/h2\u003e\n\u003cp\u003eConfigured for high-speed pulse measurement in a ControlLogix chassis, the \u003cstrong\u003eAllen-Bradley HI-1756-2DF \u003c\/strong\u003eprocesses two independent frequency inputs for controller data acquisition.\u003c\/p\u003e\n\u003ch3\u003eHardware Specifications\u003c\/h3\u003e\n\u003cfigure\u003e\n\u003ctable\u003e\n\u003cthead\u003e\n\u003ctr\u003e\n\u003cth\u003eParameter\u003c\/th\u003e\n\u003cth\u003eSpecification\u003c\/th\u003e\n\u003c\/tr\u003e\n\u003c\/thead\u003e\n\u003ctbody\u003e\n\u003ctr\u003e\n\u003ctd\u003eModel\u003c\/td\u003e\n\u003ctd\u003eHI-1756-2DF\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBrand\u003c\/td\u003e\n\u003ctd\u003eAllen-Bradley\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eManufacturer\u003c\/td\u003e\n\u003ctd\u003eRockwell Automation\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eSeries\u003c\/td\u003e\n\u003ctd\u003eControlLogix\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eModule Type\u003c\/td\u003e\n\u003ctd\u003e2-channel pulse frequency input module\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eNumber of Inputs\u003c\/td\u003e\n\u003ctd\u003e2 independent channels\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eInput Frequency Range\u003c\/td\u003e\n\u003ctd\u003e1 Hz to 250 kHz per channel\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eInput Signal Types\u003c\/td\u003e\n\u003ctd\u003eMagnetic pick-offs, open collectors, TTL, 24 VDC pulse signals\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eInput Voltage Range\u003c\/td\u003e\n\u003ctd\u003e0.2 V to 30 V peak-to-peak, channel and signal type dependent\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eChassis Location\u003c\/td\u003e\n\u003ctd\u003eAny slot in a ControlLogix 1756 chassis\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBackplane Current, 5 VDC\u003c\/td\u003e\n\u003ctd\u003eApproximately 250 mA\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eBackplane Current, 24 VDC\u003c\/td\u003e\n\u003ctd\u003eApproximately 3 mA\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePower Dissipation\u003c\/td\u003e\n\u003ctd\u003e3.5 W maximum\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eIsolation Voltage\u003c\/td\u003e\n\u003ctd\u003e500 VAC continuous, channel-to-backplane\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eTerminal Block\u003c\/td\u003e\n\u003ctd\u003e1756-TBCH or 1756-TBS6H, 36-pin\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003ePower Consumption\u003c\/td\u003e\n\u003ctd\u003e3.5 W maximum power dissipation; backplane current as specified above\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eFrequency Measurement\u003c\/td\u003e\n\u003ctd\u003eHigh-speed pulse frequency processing\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003ctr\u003e\n\u003ctd\u003eData Processing\u003c\/td\u003e\n\u003ctd\u003eFrequency and pulse signal processing independent of the main controller scan time\u003c\/td\u003e\n\u003c\/tr\u003e\n\u003c\/tbody\u003e\n\u003c\/table\u003e\n\u003c\/figure\u003e\n\u003ch3\u003eControlLogix High-Speed Pulse Processing\u003c\/h3\u003e\n\u003cp\u003eThe 1756-2DF provides two electrically independent input channels for high-frequency pulse acquisition. Each channel accepts pulse signals from magnetic pick-offs, open-collector outputs, TTL sources, or 24 VDC pulse devices.\u003c\/p\u003e\n\u003cp\u003eThe specified measurement range extends from 1 Hz to 250 kHz per channel. Therefore, the module can process frequency signals associated with flow measurement, turbine meters, tachometers, and velocity feedback applications.\u003c\/p\u003e\n\u003cp\u003eThe module communicates processed measurement data through the ControlLogix 1756 chassis backplane. Its dedicated pulse processing reduces dependence on the main controller scan interval for high-speed input acquisition.\u003c\/p\u003e\n\u003cp\u003eThe module uses approximately 250 mA from the 5 VDC backplane supply and approximately 3 mA from the 24 VDC backplane supply. Maximum power dissipation is specified as 3.5 W.\u003c\/p\u003e\n\u003ch3\u003eFrequently Asked Questions (FAQ)\u003c\/h3\u003e\n\u003cp\u003eQ: How many pulse input channels are provided by the 1756-2DF?\u003cbr\u003eA: The module provides two independent pulse frequency input channels.\u003c\/p\u003e\n\u003cp\u003eQ: What frequency range can each input process?\u003cbr\u003eA: Each channel supports an input frequency range from 1 Hz to 250 kHz.\u003c\/p\u003e\n\u003cp\u003eQ: Which terminal blocks are specified for the module?\u003cbr\u003eA: The supplied data specifies the 1756-TBCH and 1756-TBS6H 36-pin removable terminal blocks.\u003c\/p\u003e\n\u003ch3\u003eField Installation Guidelines\u003c\/h3\u003e\n\u003cul\u003e\n\u003cli\u003eInstall the module in an available slot within the specified ControlLogix 1756 chassis.\u003c\/li\u003e\n\u003cli\u003eVerify the selected field device output type before connecting it to either pulse input channel.\u003c\/li\u003e\n\u003cli\u003eConfirm the signal voltage remains within the specified 0.2 V to 30 V peak-to-peak range for the applicable input type.\u003c\/li\u003e\n\u003cli\u003eRoute pulse signal wiring separately from high-current motor, contactor, and variable-frequency drive conductors.\u003c\/li\u003e\n\u003cli\u003eUse shielded signal cable where electromagnetic interference could affect pulse waveform integrity.\u003c\/li\u003e\n\u003cli\u003eTerminate cable shields according to the plant grounding architecture and avoid creating unintended ground loops.\u003c\/li\u003e\n\u003cli\u003eMaintain correct polarity and terminal identification for each independent input channel.\u003c\/li\u003e\n\u003cli\u003eVerify the installed terminal block type before field wiring, using either the 1756-TBCH or 1756-TBS6H specified for this module.\u003c\/li\u003e\n\u003cli\u003eCheck the ControlLogix chassis power budget against the approximately 250 mA 5 VDC and 3 mA 24 VDC backplane requirements.\u003c\/li\u003e\n\u003cli\u003eInspect pulse waveform quality during commissioning when operating near the upper frequency range.\u003c\/li\u003e\n\u003cli\u003eKeep pulse wiring physically separated from noisy switching circuits to reduce false transitions and frequency measurement errors.\u003c\/li\u003e\n\u003c\/ul\u003e","brand":"AMPHENOL","offers":[{"title":"Default Title","offer_id":43921410687066,"sku":"HI-1756-2DF","price":123.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0612\/4601\/3530\/files\/HI-1756-2DF.jpg?v=1787824493","url":"https:\/\/www.plcmasters.com\/products\/allen-bradley-hi-1756-2df-controllogix-pulse-frequency-input-module","provider":"PLC Masters Ltd.","version":"1.0","type":"link"}