JXBS-3001-PH-RS

Remote pH observation with the correct JXCT register

Sankhya Farms supports the standalone JXBS-3001-PH-RS through the JXCT_pH_only profile. It polls at 9600 baud, selects the documented high-precision pH word and applies the JXCT 0.01 scale before the value reaches the free cloud dashboard. This avoids two common integrations that appear to work but are wrong: reading the lower-precision address by default, or decoding JXCT pH with the ZTS family's 0.1 multiplier.

The probe can serve as a simple observation instrument in an orchard, greenhouse, nursery, raised bed, home garden, landscape soil or container trial. A pH history is especially helpful when an amendment or a change in irrigation water is expected to act slowly. The system need not control anything; it can preserve a read-only record for later comparison. For hydroponic nutrient solutions, use an electrode assembly explicitly rated for liquid service rather than assuming that every RS-485 pH probe can remain submerged.

Which JXBS pH register should I read?

For the primary measurement, read holding register 000DH and multiply the unsigned word by 0.01 pH. The model also exposes 0006H, described here as the lower-precision pH value. Configuration uses 0100H for the slave address and 0101H for baud. A raw value of 642 at the high-precision address is pH 6.42. Sankhya stores 6.42, not the integer 642.

Why might another integration show pH ten times too high?

It may be applying the ZTS 0.1 scale to a JXCT word that requires 0.01, or it may be reading the wrong address. Match the exact manufacturer family and revision.

Can pH be logged without an irrigation system?

Yes. The node and dashboard can operate as a monitoring system only; pumps and dosing equipment are optional and separate.

Bus & electrical specs

Specs sourced from: Official JXBS-3001-TR datasheet (R208894) and JXCT manuals.

Modbus-RTU register map

Function codes 0x03 at 9600 bps, 8N1. Data registers are read with 0x03; configuration registers are written with 0x06. PLC column shows the 4xxxx Modbus holding-register convention.

How far to trust this probe's pH

In our orchard, a pH stuck near 7 turned out to be a dead electrode. Until a probe passes the test below, treat its pH as low confidence. Its moisture and EC can still be useful.

Test a JXBS-3001 pH probe

You need: neat white vinegar (pH about 2.4–3.4), borax at about one level teaspoon per litre of water (pH about 9.2), clean water for rinsing, two cups at least 10 cm deep, and a pen pH meter to check each liquid.

1. Keep both cups in the shade. In direct sun a cup reached 52 °C, and the readings jumped.
2. Power the probe for 5 minutes before the first reading. The manual gives no warm-up time, so we use the same wait as our field firmware.
3. Put the probe in the neat vinegar. Check the cup with the pen, then wait until the reading stops moving, about an hour. Note the value.
4. Rinse the probe in clean water. Put it in the borax, check the cup with the pen, wait until it settles, and note the value.
5. Read the result from the later reading in each cup, because the first can still be settling. A working probe reads close to 3 in the vinegar and close to 9 in the borax, so a swing of at least 4 pH is a pass. A dead probe stays between about 5.6 and 7.8, or at exactly 7.00 in both cups.
6. Don't use diluted vinegar. In hard water, a splash can sit anywhere from pH 4 to 7.

A pass means the electrode responds. Its pH is still low confidence until you check it against your pen readings with a two-point calibration. A fail means the electrode is dead: replace the probe, and don't use its pH in the meantime.

Changing address & baud rate

This probe is configured over the same RS-485 bus using Modbus write commands (function code 0x06). Configure one device at a time on the bus.

• Set the Modbus slave address by writing register 0100H (PLC 40257) with function code 0x06. Range 0-252. Factory default 1.
• Set the baud rate by writing register 0101H (PLC 40258). Values: 2400=2400, 4800=4800, 9600=9600. Factory default 9600 bps.
• Power-cycle the probe after a configuration write for the change to take effect.

Notes & caveats

Confirmed from official JXCT PDF (v2.0, 2020-10-24). Default baud 9600 (not 4800). Power 12-24V (not 5-24V). Long-term stability ≤5%/year. Two pH registers — use 000DH (high precision) as primary. JXCT config register layout (0100H/0101H) confirmed.

Common questions

What baud rate does the JXBS-3001-PH-RS use by default?

9600 bps, 8N1. It is a Modbus-RTU slave; default address 1.

What supply voltage does the JXBS-3001-PH-RS need?

DC 12–24 V (≤ 0.15 W (12 V DC)).

How do I change the JXBS-3001-PH-RS Modbus address?

Write the device-address register with function code 0x06, one device on the bus at a time, then power-cycle. See the Configuration section above.

Is the JXBS-3001-PH-RS compatible with the Sankhya platform?

Yes — it is in the Sankhya RS-485 sensor library and the firmware-generation pipeline can produce node firmware for it.

What does the JXBS-3001-PH-RS not measure?

The JXBS-3001-PH-RS reports pH only — it does not report moisture, temperature, EC, N-P-K, salinity and TDS. On the same RS-485 bus, add moisture: JXBS-3001-TR (4-in-1); temperature: JXBS-3001-TR (4-in-1); EC: JXBS-3001-TR (4-in-1).

Can I trust this probe's pH readings?

Not yet, from our field tests. A pH stuck near 7 can mean a dead electrode, and a 7.00 means no reading. Test the probe in neat vinegar and borax (see Field test) before relying on its pH.

How many Modbus registers does the JXBS-3001-PH-RS expose?

This guide documents 4 registers, read with function code 0x03 and written with 0x06 where the register is RW. Documented entries include Low-precision pH, High-precision pH, Device address and Baud rate.

How this differs from similar models

How the JXBS-3001-PH-RS compares with the other RS-485 models in the Sankhya library. "Drop-in" means the same parameter set and the same register map, read by the same firmware profile.

Related JXCT sensors