Hach 3798-S sc
Digital inductive conductivity sensor, read through a Hach sc controller with a Modbus RS485 module.
The Hach 3798-S sc is a digital inductive conductivity sensor that measures soiled to heavily soiled water, such as drain water in greenhouses, and connects to a Hach sc controller. This Modbus RTU template reads conductivity, resistivity, temperature and the error and status words, and lets you write temperature compensation, reference temperature and log settings from ModbusCloud.
- Protocol
- Modbus RTU
- Connection
- RS485, 19200 baud
- Registers
- 68, read and write
- Brand
- Hach
- Key readings
- Conductivity · Temperature · Resistivity · Calibration slope · Error and status word
- Available commands
- Temperature compensation · Compensation coefficient · Reference temperature · Manual temperature · Log intervals
- Compatible models
- 3798-S sc V2 (LXV428.99.00001)
- Last updated
Registers (68)
68 read, 31 write
| Name | Unit | Access | Address (Hidden until you enter your email) | Function (hidden) | Type (hidden) |
|---|---|---|---|---|---|
| Conductivity mS/cm | mS/cm | Read | |||
| Conductivity µS/cm | µS/cm | Read | |||
| Temperature | Read | ||||
| Conductivity S/cm | Read | ||||
| Conductivity S/m | Read | ||||
| Conductivity mS/m | Read | ||||
| Resistivity Ohm cm | Read | ||||
| Resistivity kOhm cm | Read | ||||
| Resistivity Ohm m | Read | ||||
| Resistivity Ohm m 2 | Read | ||||
| Raw Temperature | Read | ||||
| Auto Range S/cm | Read | ||||
| Auto Range S/m | Read | ||||
| Auto Range Ohm cm | Read | ||||
| Auto Range Ohm m | Read | ||||
| Temporary Measurement 0 | Read | ||||
| Temporary Measurement 1 | Read | ||||
| Output Voltage | Read | ||||
| Time From Start Up | Read | ||||
| Time of Humidity Bag | Read | ||||
| Classified Error Word | Read | ||||
| Classified Status Word | Read | ||||
| Offset Correction | Read | ||||
| Electrical Calibration Resistance | Read and write | ||||
| Electrical Slope | Read | ||||
| Process Slope | Read and write | ||||
| Main Calibration Adjust Value | Read and write | ||||
| Second Calibration Adjust Value | Read and write | ||||
| Cell Constant | Read and write | ||||
| Calibration Code | Read and write | ||||
| Delay From Last Calibration | Read and write | ||||
| Temperature Compensation | Read and write | ||||
| Compensation Coefficient | Read and write | ||||
| Temperature Reference | Read and write | ||||
| Automatic Temperature | Read and write | ||||
| Manual Temperature | Read and write | ||||
| Temperature Offset | Read and write | ||||
| Conductivity Unit | Read and write | ||||
| Temperature Unit | Read and write | ||||
| Conductivity Parameter | Read and write | ||||
| Temperature Unit Command | Read and write | ||||
| Output Mode | Read and write | ||||
| Averaging | Read and write | ||||
| Mains Frequency | Read and write | ||||
| Conductivity Log Interval | Read and write | ||||
| Temperature Log Interval | Read and write | ||||
| Analogue Output Command | Read and write | ||||
| Password | Read and write | ||||
| Function Code | Read and write | ||||
| Next State | Read | ||||
| Main Measurement Tag | Read | ||||
| Second Measurement Tag | Read | ||||
| Calibration Main Measurement Tag | Read | ||||
| Calibration Second Measurement Tag | Read | ||||
| Calibration Main Adjust Value Tag | Read | ||||
| Calibration Second Adjust Value Tag | Read | ||||
| Temporary Measurement 0 Tag | Read | ||||
| Temporary Measurement 1 Tag | Read | ||||
| Temperature Offset Correction Tag | Read | ||||
| Temperature Reference Tag | Read and write | ||||
| Manual Temperature Tag | Read and write | ||||
| Sensor Name | Read and write | ||||
| Serial Number Text | Read | ||||
| Serial Number Word 1 | Read and write | ||||
| Serial Number Word 2 | Read and write | ||||
| Serial Number Word 3 | Read and write | ||||
| Software Version | Read | ||||
| Driver Version | Read |
Loading registers…
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If a device is not in the library yet, we build the template for free as soon as we have the register data.
Use cases
- Show the EC of drain water in mS/cm on a dashboard next to pH and the supply water values.
- Get an email or webhook alert when conductivity rises above the limit you set for the drain water.
- Alert on an error word that is not 0, so a sensor or calibration fault reaches you right away.
- Keep 365 days of conductivity history to compare drain water between crops, weeks and seasons.
- Check the compensation coefficient and reference temperature remotely when readings differ from a hand meter.
Installation
Fit the Modbus RS232/RS485 module in the Hach sc200 or SC4500 controller and set its switches to RS485, with termination on at the end of the bus.
Wire RS485 A and B of the module to A and B of the ModbusCloud Gateway and terminate both ends of the bus.
In the controller's Modbus settings, set or note the Modbus address of the 3798-S sc. Keep 19200 baud, RTU, no parity, 1 stop bit and data order Little Endian.
In ModbusCloud, add a Modbus device with the address of the sensor and the same serial settings, then import this template.
Check that conductivity and temperature match the controller display.
Things to watch for
The sensor does not answer. What should I check?
Every sensor answers on its own Modbus address, not on the address of the controller or the module. Check the address of this sensor in the controller's Modbus settings, the serial settings (19200 baud, no parity, 1 stop bit by default), that switch 4 on the module selects RS485 and that A and B are not swapped. The template needs the RS485 module; it does not work over SC4500 Modbus TCP.
Conductivity shows huge or tiny numbers. Why?
The template expects the factory data order of the Modbus module, Little Endian. When the data order in the controller is set to Big Endian, the two halves of every value are swapped. Set the data order back to Little Endian. On an SC1000 with virtual slaves, scrambled values point to a different word order.
Why are mS/cm and temperature right while the other units look shifted?
The template fits 3798-S sc sensors with software V2. Read the Software Version register or check the sensor information on the controller. With other sensor software the values after temperature can sit at different positions.
Which conductivity value should I use?
All conductivity registers carry the same measurement in a different unit. For irrigation and drain water mS/cm is the usual choice; µS/cm suits low values. Temperature is shown without a unit, because the sensor can be set to °C or °F.
Can I write settings from ModbusCloud safely?
A write changes the sensor configuration directly, the same as the controller menu. Read the current value first and change one setting at a time; a wrong compensation coefficient or reference temperature shifts every conductivity value. Register writing is off per gateway until you request it.
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