Configuring Omron C200H-AD002 for 0–50 kgf/cm² BCD Scaling

Configuring the Omron C200H-AD002 for 0–50 kgf/cm² BCD Scaling

This field-procedure guide covers a recurring commissioning task on the legacy Omron C200H platform: reading an industrial pressure transmitter (0–50 kgf/cm²) through a C200H-AD002 analog input module and delivering the engineering value to a downstream display or indicator in BCD (Binary Coded Decimal) format. The C200H-AD002 is an 8-bit-resolution/12-bit-converter special I/O card with on-board scaling that maps a raw A/D count (0–4095) to a user-defined engineering range held in DM. When the engineering range is written in BCD, the card returns a scaled BCD word that can be driven straight onto a BCD-display indicator or transferred directly into a thumbwheel-style data table.

The article is written for automation engineers who still maintain C200H, CS1, or CJ2 retrofits that need a clean 00.00–50.00 process value in BCD without writing ladder math for each project. It assumes the transmitter is a 1–5 V or 4–20 mA type — the scaling equations below cover both. Where the original Omron manual W229-E1-3 is the authoritative reference for DM mapping, this guide extracts only the operational subset and adds the calculation discipline and ladder snippets needed for an actual install.

1. Hardware Overview: C200H-AD002

The C200H-AD002 is a 4-point analog input special I/O module mounted to a C200H (or CS1/CJ1 with adapter) backplane. It digitises each channel to 12 bits and exposes the result as 0–4095 counts. The card accepts:

• 0–10 V voltage input
• 1–5 V / 4–20 mA current/voltage input (with the 4–20 mA conversion by external 250 Ω resistor)
• ±10 V bipolar (sign-magnitude output in DM)

Confirm the card's catalog number on the side label before proceeding; the C200H-AD001 (8-point, no scaling) and C200H-AD003 (8-point, isolated) are electrically similar but their DM area layouts differ. The procedure below applies only to the AD002.

2. Prerequisites

1. C200H-AD002 mounted on a CPU backplane and assigned a Special I/O Unit Number using the rotary DIP switch on the card front (0–F). Set it to 0 unless you already have units 0–1 populated.
2. Pressure transmitter calibrated 0–50 kgf/cm², output 1–5 V (or 4–20 mA with 250 Ω precision resistor).
3. CX-Programmer (or SYSWIN / LSS for legacy laptops) connected via the CPU peripheral port or serial unit.
4. Wiring: shielded twisted pair, shield grounded at the panel end only, channel commons isolated per manual section 4.
5. Power-on cycle access — DM parameters only take effect after the unit is restarted.

3. DM Word Map for Unit Number 0

The crucial register is D1005: writing the BCD literal #5000 tells the AD002 to map the maximum raw A/D count (4095) to engineering value 50.00, while D1003 = #0000 maps the minimum raw count (0) to 00.00. Because the card performs the linear interpolation internally and emits the result as a BCD word directly in its allocated IR word, the ladder does not have to call SCL(194) or SCL2(486) at all.

4. Scaling Math: Why 50.00 kgf/cm² Becomes #5000

The transmitter outputs 1–5 V over 0–50 kgf/cm². The AD002 with range code 2 reads 1 V as 0 counts (live zero suppression happens inside the card) and 5 V as 4095 counts. The scaling equation the card applies internally is:

Scaled = ((Raw − Raw_min) × (B − A)) / (Raw_max − Raw_min) + A

where:

• Raw = A/D count, 0–4095
• A = lower display scaling value (D1003 = 0)
• B = upper display scaling value (D1005 = 5000)
• Raw_min = 0, Raw_max = 4095

With A = 0 and B = 5000, the equation collapses to:

Scaled = Raw × 5000 / 4095

Examples:

5. Configuration Procedure

5.1 Set the Special I/O Unit Number

1. Power off the rack.
2. Set the rotary switch on the AD002 front face to 0 (use a small flat-blade).
3. Power on.

5.2 Write DM Parameters Online

From CX-Programmer, connect online and use the forced-set / monitor window. Do not write to DM while the unit is live — the writes only commit at the next power cycle.

1. Open the DM area editor, navigate to D1000.
2. Enter each word in BCD as listed in the table above.
3. Confirm by reading D1000–D1009; the values must echo what you just wrote.
4. Cycle power to the CPU.
5. Reconnect online and verify the words are still present after the cycle.

5.3 Verify Range Code with a Calibrator

Apply 1.000 V to channel 0 from a precision calibrator. Read IR word CIO 100 (unit 0 input area, channel 1) — it must read 0x0000 (BCD 0000). Apply 5.000 V; the same word must read 0x5000 (BCD 5000). If the value stops at 0x4000 the range code was wrong; the card is treating the input as 0–5 V not 1–5 V.

6. Ladder: Reading the Scaled BCD Word

When the DM scaling is set up correctly, the AD002 delivers the scaled BCD value into the IR area directly. For unit number 0, channel 1 the IR word is CIO 100; channels 2–4 are CIO 101 through CIO 103. The ladder below reads the value, applies an alarm comparison, and outputs it to a BCD display module:

 |           MOV(021)         |
 |   CIO100     D00200        |
 |                           |
 |           CMP(020)        |
 |   D00200    #4500    P_EQ |
 |                           |
 |  |--(P_EQ)-----OUT CIO 200.00   ; HI PRESSURE LAMP
 |                           |
 |           BCD(024)        |
 |   D00200     D00210       |
 |                           |
 |           BIN(023)        |
 |   D00210     D00300       |

Notes:

• MOV(021) copies the pre-scaled BCD word out of the input area into a general-purpose DM word D200 so it is preserved across scans.
• CMP(020) compares D200 against #4500 (45.00 kgf/cm²) and energises the P_EQ bit when equal; a contact on that bit drives a lamp.
• BCD(024) converts the BCD word to binary for any downstream integer math (PID block, setpoint comparison, etc.).
• BIN(023) is included as a round-trip example for downstream math that needs the binary form; the original BCD is still in D200.

7. Alternative: Using SCL2(486) in the Ladder Instead of DM Scaling

If you want to keep the AD002 in raw-binary mode and do the scaling in ladder (e.g. for a CS1 where you might re-allocate the unit number frequently), use SCL2(486). Place a raw-binary copy of CIO 100 into D100, then:

 |           SCL2(486)        |
 |   D0100    D00110  D00200 |
 |                           |

Where D110 holds the scaling parameters (each pair of words is one parameter):

SCL2(486) requires the parameters in BCD but the raw input in binary; D100 is binary from the card. Output D200 is BCD. This is functionally equivalent to the DM-scaling approach and is the method you must use on a CS1 if the AD002 unit number is later changed and you do not want to cycle power to refresh DM.

8. Verification Checklist

9. Troubleshooting Matrix

10. Field-Proven Caveats

• The C200H-AD002 uses 1-based IR numbering for the special I/O area; for unit 0 the channels occupy CIO 100–CIO 103. For unit 1 they shift to CIO 110–CIO 113. The DM block always starts at D1000 + 10 × unit_number regardless of CPU type.
• If your transmitter is 4–20 mA, fit a 250 Ω, 0.1 % precision resistor across the input terminals. This converts 4 mA to 1 V and 20 mA to 5 V; the AD002 sees the same 1–5 V signal as a voltage input.
• BCD scaling is unsigned on the C200H-AD002. Negative pressures must be handled either by using the bipolar ±10 V range (range code 6) or by adding an offset in ladder using ADD(030) after scaling.
• The DM block is shared with the CX-Programmer upload tool. If you save the project to the SD card of a CS1, ensure DM retention is enabled so the scaling does not reset on power-up.
• Do not edit D1000–D1009 every scan from ladder. The card only samples them at startup, so any runtime change is ignored — and the periodic write causes scan-time expansion.
• For applications requiring CE/UL compliance on a new install, the C200H-AD002 is end-of-life; use the CS1W-AD081-V1 with equivalent ladder-side SCL2(486) and a BCD output module.

11. Frequently Asked Questions