Part of the Omron CJ-Series PLCs series — see the full model table, lifecycle status and replacement parts.
Omron CJ1W-CT021 — 2 Channel Counter
SKU: CJ1W-CT021USD 160.00
CJ-series 2-channel high-speed counter, 500 kHz line-driver / 50 kHz open-collector, 32-bit range, 2 in / 2 out.
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Product Overview
The Omron CJ1W-CT021 is a Special I/O unit that adds two independent 32-bit counters to any CJ-series PLC. It is manufactured by Omron Corporation. Hengyixin Automation stocks this timer in Xiamen and ships within 3-5 business days to most Asian, European, and North American ports. Specifications on this page were checked against Omron's CJ1W-CT021 datasheet (Cat. No. W401).
0.5 ms response for high-speed closed-loop control 500 kHz max input with RS-422 line driver, 50 kHz with open-collector 32-bit signed count range (-2,147,483,648 to +2,147,483,647) 2-channel high-speed counter for CJ-series Special I/O rack slot
Key specs: Unit Type CJ-series Special I/O high-speed counter; Counter Channels 2 independent; Maximum Input Frequency 500 kHz line driver / 50 kHz open-collector; Count Range 32-bit (-2,147,483,648 to +2,147,483,647); Input Signal Levels DC 5 V, 12 V, or 24 V (selectable per axis); Digital Inputs 2 total (I0 and I1), assignable to either counter; Digital Outputs 2 total (O0 and O1), open collector, NPN or PNP selectable per output; plus 30 internal soft outputs; Counter Modes Simple, ring, linear.
Key Features
- 0.5 ms response for high-speed closed-loop control
- 500 kHz max input with RS-422 line driver, 50 kHz with open-collector
- 32-bit signed count range (-2,147,483,648 to +2,147,483,647)
- 2-channel high-speed counter for CJ-series Special I/O rack slot
- SKU: CJ1W-CT021
- Series: CJ1W-CT021
Best-Fit Applications
- Position control on rotary index tables driven by an E6B2 / E6C2 encoder
- Length / stroke measurement on linear cylinders with a tethered encoder
- RPM and line-speed measurement on rotating shafts
Buying Checklist
- Choose CJ1W-CT021 for 2 channels of high-speed counting (500 kHz line driver).
- Pick CJ1W-CT041 if you need 4 channels in one slot.
- Confirm encoder type (NPN open-collector vs PNP line driver) before ordering.
Technical Specifications
| Unit Type | CJ-series Special I/O high-speed counter |
|---|---|
| Counter Channels | 2 independent |
| Maximum Input Frequency | 500 kHz line driver / 50 kHz open-collector |
| Count Range | 32-bit (-2,147,483,648 to +2,147,483,647) |
| Input Signal Levels | DC 5 V, 12 V, or 24 V (selectable per axis) |
| Digital Inputs | 2 total (I0 and I1), assignable to either counter |
| Digital Outputs | 2 total (O0 and O1), open collector, NPN or PNP selectable per output; plus 30 internal soft outputs |
| Counter Modes | Simple, ring, linear |
| Current Draw | 280 mA at 5 VDC |
| Dimensions (W x H x D) | 31 × 95.4 × 83.6 mm |
| Weight | 94 g |
| Compatible PLCs | CJ1H, CJ1M, CJ2H, CJ2M, NJ |
| Soft Outputs | 30 internal soft outputs, driven by counter value zone and target comparisons, delays, holds and hysteresis settings |
Manufacturer documentation
Omron's own product page, where the manufacturer's current specification and lifecycle information are published. We are an independent distributor and cannot mirror those documents; the link goes to Omron's site.
FAQ for CJ1W-CT021
What is the difference between the CJ1W-CT021 and the C200H-CT021?
The CJ1W-CT021 is the CJ-series Special I/O drop-in replacement for the C200H-CT021. Both are 2-channel 500 kHz high-speed counters with the same connector pinout, the same CX-Programmer counter-parameter map, and the same 32-bit count range. Use the CJ1W-CT021 on a CJ or CS rack; keep the C200H-CT021 only on legacy C200H Alpha or C200HS racks that are not slated for replacement.
Can the CJ1W-CT021 mount on an NJ-series PLC?
Yes, the CT021 mechanically fits and is recognised by an NJ-series CPU, but several advanced features are disabled on NJ: pulse-rate measurement, capture values into the CIO area, the external-control input capture / stop-capture-continue / stop-capture-reset-continue / capture-reset modes, the pulse-rate range control mode, and the IORD / IOWR ladder instructions. If you need those, drop back to a CJ1H / CJ1M / CJ2 CPU.
How does the CT021 connect to a 24 VDC NPN encoder like the E6B2-CWZ6C?
Terminal A8 is encoder phase A, A10 phase B, A12 phase Z. The encoder brown wire (V+) goes to terminal B9 / B11 / B13 and the encoder blue wire goes to common. Quadrature decoding is automatic: count direction follows phase A and phase B relative timing, and phase Z is the configurable reset / preset / capture trigger.
Can the CT021 replace the high-speed counter that is built into a CJ1M-CPU21 or CJ1M-CPU22?
Yes, when you exceed 100 kHz or need the linear / ring modes plus capture and preset that the CJ1M built-in HSC does not offer. The built-in HSC plus the CT021 can also run side-by-side: the built-in HSC keeps the legacy single-axis 100 kHz counter for the fast local inputs, and the CT021 takes over on a separate channel.
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