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          Apter Power supplies 6ES7421-1FH20-0AA0 quotations, technical manuals, and product-selection support.

        6ES7421-1FH20-0AA0

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        1001 reviews ｜ Need a Specific Revision?
        Siemens 6ES7421-1FH20-0AA0 is an isolated S7-400 SM421 input module with sixteen 120/230 V AC/DC channels organized in groups of four.
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        We provide 1 year warranty for all remaining parts.
        The warranty period is one year from the date of shipment, unless otherwise stated in the parts description. We guarantee that the project will not exhibit functional defects that may occur under normal operating conditions during the warranty period.
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        The warranty period is one year from the date of shipment, unless otherwise stated in the parts description. We guarantee that the project will not exhibit functional defects that may occur under normal operating conditions during the warranty period.
        In the event of a defect, we will send new equipment, repair equipment or refund the purchase price based on our availability. You must contact us to obtain a return authorization and return the defective device to us within 14 days of reporting the defect.
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        Technical specifications for 6ES7421-1FH20-0AA0

        • Manufacturer:
          Siemens
        • Part Number:
          6ES7421-1FH20-0AA0
        • Product Family:
          Siemens Simatic S7-400
        • Product Type:
          SIMATIC S7-400 SM421 UC Digital Input Module
        • Stock:
          1
        • Digital Inputs:
          16
        • Input Signal Type:
          120/230 V AC/DC
        • AC Frequency:
          47 to 63 Hz
        • Signal 0 Range:
          0 to 40 V AC or -40 to +40 V DC
        • Signal 1 Range:
          74 to 264 V AC or 80 to 264 V DC
        • Input Delay, 0 to 1:
          20 ms maximum
        • Input Delay, 1 to 0:
          30 ms maximum
        • Shielded Cable Length:
          1000 m maximum
        • Unshielded Cable Length:
          600 m maximum
        • Two-Wire Sensor Current:
          5 mA AC maximum
        • Isolation Groups:
          4 channels per group
        • Isolation Test Voltage:
          1500 V AC
        • Status Indication:
          Green LED per input
        • Module Diagnostics:
          Not provided
        • Backplane Current:
          80 mA maximum
        • Power Loss:
          12 W
        • Weight:
          1.711 lbs (0.776 kg)
        • Estimated shipping dimensions:
          30.2x22.9x4.1cm
        • Tariff Code:
          8538909100
        • Country of origin:
          Germany
        • Place of shipment:
          Xiamen,Fujian,China
        By purchasing this item, you agree to the Terms & Conditions, ApterPower is not an authorized distributor for listed manufacturers or tradenames and therefore the manufacturer's warranty does not apply. All our products come with ApterPower's 1-year warranty.

        More Information

        Overview Manuals Input Levels Isolation Field Wiring Channel Status

        Features:

        • Sixteen high-voltage input points connect field states to the S7-400 backplane.
        • Four-channel isolation groups divide field references without splitting the front status display.
        • Defined AC/DC thresholds and transition delays determine when each channel changes its process-image state.
        The absence of onboard diagnostics on 6ES7421-1FH20-0AA0 makes the channel LED and terminal measurement central to fault isolation.

        Cable-length limits on 6ES7421-1FH20-0AA0 differ for shielded and unshielded field conductors.

        Two-wire sensor leakage on 6ES7421-1FH20-0AA0 must remain below the off-state current boundary to avoid a false input.

        The Siemens 6ES7421-1FH20-0AA0 SIMATIC S7-400 SM421 Digital Input Module may still be available for purchase and support from Apter Power beyond End-Of-Life (EOL) by the manufacturer (OEM).
        Siemens 6ES7421-1FH20-0AA0 SIMATIC S7-400 SM421 Digital Input Module Manuals,Datasheets,Link Important Notice: Other accessories, manuals, cables, calibration data, software, etc. are not included with this equipment unless listed in the above stock item description. All prices are shown in USD.

        AC/DC State Recognition

        • Signal zero: Low AC or bipolar DC voltage remains inside the documented zero range.
        • Signal one: The upper AC/DC range is interpreted as an active input.
        • Rising delay: A zero-to-one change can require as much as 20 ms.
        • Falling delay: A one-to-zero change can require as much as 30 ms.

        Four-Channel Group Boundary

        • Grouping: The sixteen channels are divided into groups of four.
        • Reference: Each group preserves its assigned field-potential relationship.
        • Backplane: Isolation separates field circuitry from the controller backplane.
        • Test level: The documented isolation test uses 1500 V AC.

        Sensor and Cable Limits

        • Shielded run: A shielded field connection can extend to 1000 m under the stated conditions.
        • Unshielded run: An unshielded field connection is limited to 600 m.
        • Two-wire sensor: Off-state current remains within 5 mA AC to preserve signal zero.
        • Frequency: AC field signals remain within the documented 47 to 63 Hz range.

        Local Indication and Checks

        • Input LEDs: One green indicator follows each accepted channel state.
        • No diagnostics: The module does not generate its own diagnostic message set.
        • Terminal check: Voltage is measured at the affected input and group reference.
        • Backplane state: The controller process image is compared with the local LED during troubleshooting.
        Description
        Siemens 6ES7421-1FH20-0AA0 is a SIMATIC S7-400 SM421 digital input module that brings sixteen 120/230 V AC/DC field states into the controller. The channels are isolated in groups of four, so each group maintains its documented field reference while the backplane receives processed input data.

        Each channel of 6ES7421-1FH20-0AA0 interprets 0 to 40 V AC or -40 to +40 V DC as signal zero and the documented higher range as signal one. The input path can require up to 20 ms for a zero-to-one transition and 30 ms for a one-to-zero transition.

        Field conductors on 6ES7421-1FH20-0AA0 may extend to 1000 m with shielded cable or 600 m with unshielded cable under the stated conditions. Two-wire sensors are supported when their off-state current remains within the 5 mA AC limit.

        The green front indicators of 6ES7421-1FH20-0AA0 display the accepted state of each input without providing module diagnostics. Its 25 x 290 x 210 mm format occupies the S7-400 module position and draws no more than 80 mA from the backplane.
        Alternative Names
        6ES74211FH200AA0 6ES7421 1FH20 0AA0 6ES 7421 1FH20 0AA0 Siemens 6ES7421-1FH20-0AA0 6ES7421-1FH20-0AA0 SM421 6ES7421-1FH2O-OAAO 6ES742I-1FH20-0AA0 6ES7421-IFH20-0AA0
        Technical notes
        Sixteen high-voltage input channels, four-channel isolation groups, defined signal thresholds, and individual LEDs characterize Siemens 6ES7421-1FH20-0AA0.
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        FAQS

        The following is a list of questions commonly asked by our customers. Please contact us if you have a question about our process that is not answered below.
        VIEW ALL FAQS
        Why does an input LED on 6ES7421-1FH20-0AA0 remain off with field voltage present?
        Measure the 6ES7421-1FH20-0AA0 channel-to-group reference voltage, confirm the signal-one threshold, frequency, wiring, and front connector.
        What causes a false active state on 6ES7421-1FH20-0AA0?
        Check the 6ES7421-1FH20-0AA0 two-wire sensor leakage, induced voltage, shared reference, cable routing, threshold, and channel assignment.
        Why are four adjacent channels of 6ES7421-1FH20-0AA0 inactive?
        Inspect the 6ES7421-1FH20-0AA0 four-channel group reference, connector seating, field supply, conductor continuity, and group isolation boundary.
        How should a long field cable be evaluated for 6ES7421-1FH20-0AA0?
        Compare the 6ES7421-1FH20-0AA0 cable shielding, 1000 m or 600 m limit, routing, induced voltage, sensor current, and signal threshold.
        Why does the controller state lag the field contact on 6ES7421-1FH20-0AA0?
        Allow for the 6ES7421-1FH20-0AA0 input delay, then inspect contact bounce, AC waveform, voltage threshold, scan time, and process-image use.
        How are faults isolated when 6ES7421-1FH20-0AA0 provides no module diagnostics?
        Compare the 6ES7421-1FH20-0AA0 LED, terminal voltage, group reference, front connector, process-image bit, and known-good channel.

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