Scaled value while reading Modbus

General
1

Hey,

I tried to find some answers here in the forum but without sucsess.

I am reading a value from a dosingpump. I manage to get the raw (DEZ) value. For example as in the image below: 26032. But this value is somehow scaled to another value, which is correctly displayed on the pump: The pump display here 878 ml/ h, which is the corret value
Here is a small image from the software of the dosing pump:

sasa
sasa1814Ă—63 3.23 KB

Here is my flow:

[
    {
        "id": "40353ef1cf303d73",
        "type": "modbus-flex-getter",
        "z": "776cf9194f6008fb",
        "name": "",
        "showStatusActivities": false,
        "showErrors": false,
        "logIOActivities": false,
        "server": "0e3ec676f3e39293",
        "useIOFile": false,
        "ioFile": "",
        "useIOForPayload": false,
        "emptyMsgOnFail": false,
        "keepMsgProperties": false,
        "x": 560,
        "y": 240,
        "wires": [
            [
                "57de69c1fdcc80b9",
                "1a39356543e7b1ea"
            ],
            []
        ]
    },
    {
        "id": "57de69c1fdcc80b9",
        "type": "modbus-response",
        "z": "776cf9194f6008fb",
        "name": "",
        "registerShowMax": 20,
        "x": 570,
        "y": 280,
        "wires": []
    },
    {
        "id": "eb5d2c0cd8ba7a73",
        "type": "function",
        "z": "776cf9194f6008fb",
        "name": "R_207_Batchvolume",
        "func": "msg.payload =\n{ value: msg.payload, \n'fc': 3, \n'unitid': 0, \n'address': 110, \n'quantity':1 \n    \n} ;\nreturn msg",
        "outputs": 1,
        "noerr": 0,
        "initialize": "",
        "finalize": "",
        "libs": [],
        "x": 320,
        "y": 280,
        "wires": [
            [
                "40353ef1cf303d73"
            ]
        ]
    },
    {
        "id": "e92a8786fb25e7d8",
        "type": "inject",
        "z": "776cf9194f6008fb",
        "name": "",
        "props": [
            {
                "p": "payload"
            },
            {
                "p": "topic",
                "vt": "str"
            }
        ],
        "repeat": "2",
        "crontab": "",
        "once": false,
        "onceDelay": 0.1,
        "topic": "",
        "payload": "",
        "payloadType": "date",
        "x": 130,
        "y": 280,
        "wires": [
            [
                "eb5d2c0cd8ba7a73"
            ]
        ]
    },
    {
        "id": "3990b57a3e45d703",
        "type": "debug",
        "z": "776cf9194f6008fb",
        "name": "",
        "active": true,
        "tosidebar": true,
        "console": false,
        "tostatus": false,
        "complete": "payload",
        "targetType": "msg",
        "statusVal": "",
        "statusType": "auto",
        "x": 1070,
        "y": 240,
        "wires": []
    },
    {
        "id": "1a39356543e7b1ea",
        "type": "buffer-parser",
        "z": "776cf9194f6008fb",
        "name": "",
        "data": "payload",
        "dataType": "msg",
        "specification": "spec",
        "specificationType": "ui",
        "items": [
            {
                "type": "uint16be",
                "name": "Batchvolume",
                "offset": 0,
                "length": 1,
                "offsetbit": 0,
                "scale": "0",
                "mask": ""
            }
        ],
        "swap1": "",
        "swap2": "",
        "swap3": "",
        "swap1Type": "swap",
        "swap2Type": "swap",
        "swap3Type": "swap",
        "msgProperty": "payload",
        "msgPropertyType": "str",
        "resultType": "keyvalue",
        "resultTypeType": "return",
        "multipleResult": false,
        "fanOutMultipleResult": false,
        "setTopic": true,
        "outputs": 1,
        "x": 830,
        "y": 240,
        "wires": [
            [
                "3990b57a3e45d703"
            ]
        ]
    },
    {
        "id": "0e3ec676f3e39293",
        "type": "modbus-client",
        "name": "CIM500",
        "clienttype": "tcp",
        "bufferCommands": true,
        "stateLogEnabled": false,
        "queueLogEnabled": false,
        "tcpHost": "10.240.6.39",
        "tcpPort": "502",
        "tcpType": "DEFAULT",
        "serialPort": "/dev/ttyUSB",
        "serialType": "RTU-BUFFERD",
        "serialBaudrate": "9600",
        "serialDatabits": "8",
        "serialStopbits": "1",
        "serialParity": "none",
        "serialConnectionDelay": "100",
        "serialAsciiResponseStartDelimiter": "0x3A",
        "unit_id": "1",
        "commandDelay": "1",
        "clientTimeout": "1000",
        "reconnectOnTimeout": true,
        "reconnectTimeout": "2000",
        "parallelUnitIdsAllowed": true
    }
]

I am asking myself if it is some buffer parser related problem or did the company scaled this value with a function?

Anyone an idea?

Thank you

2

What do the docs for the device say?

3

Hello.

Unfortunly i cant find any mentions in the docu about that.
Ive got a bit suspicious about the factor 0.1 that is present in the software. See image attached.

I have no idea how the number 9464 (that i can read from the modbus register) converts to 7500.

sasa
sasa1899Ă—64 3.92 KB

thank you

4

Some background:

  • Modbus Registers are always 16 BIT
  • That image shows you that 2 registers make up the HI and LO parts of the DosingCapicty
    • This leads me to think the data is either 32bit FLOAT or 32bit UINT
  • Most manufacturers of Modbus devices store 32bit data in Big Endian - so I chose the Buffer-Parser type UINT32BE meaning take 8 bytes (aka 2x16 bit values aka 32bits) of data from the incoming data & convert them to a 32Bit Unsigned Integer using Big Endian format

When you convert the 2 16 bit values [1, 9464] into a 32Bit number (Big Endian) you get 75000

When you scale that by 0.1 (or more accurately divide it by 10) you get 7500

Demo...

image
image740Ă—164 10.9 KB

Buffer Parser

image
image1082Ă—537 35.3 KB

Demo Flow

[{"id":"37600721f03d9680","type":"inject","z":"08c327c2653de72a","name":"fake mobus data R300~R303","props":[{"p":"payload"},{"p":"topic","vt":"str"}],"repeat":"","crontab":"","once":false,"onceDelay":0.1,"topic":"","payload":"[0, 0, 1, 9464]","payloadType":"json","x":1720,"y":100,"wires":[["d250bf3bda890004"]]},{"id":"d250bf3bda890004","type":"buffer-parser","z":"08c327c2653de72a","name":"","data":"payload","dataType":"msg","specification":"spec","specificationType":"ui","items":[{"type":"uint32be","name":"R300","offset":0,"length":1,"offsetbit":0,"scale":"/ 10.0","mask":""},{"type":"uint32be","name":"DosingCapacityMax","offset":4,"length":1,"offsetbit":0,"scale":"/ 10.0","mask":""}],"swap1":"","swap2":"","swap3":"","swap1Type":"swap","swap2Type":"swap","swap3Type":"swap","msgProperty":"payload","msgPropertyType":"str","resultType":"keyvalue","resultTypeType":"return","multipleResult":false,"fanOutMultipleResult":false,"setTopic":true,"outputs":1,"x":1680,"y":160,"wires":[["4c6fa20bd13e4f9d"]]},{"id":"4c6fa20bd13e4f9d","type":"debug","z":"08c327c2653de72a","name":"debug 152","active":true,"tosidebar":true,"console":false,"tostatus":false,"complete":"payload","targetType":"msg","statusVal":"","statusType":"auto","x":1880,"y":160,"wires":[]}]
2 Likes
5

Here comes a (very) long shot:

You're reading a 2 register value ... thus the calculation is like:

65536 * [Reg 302] + [REG 303] = 75000

[edit] ... as Steve explained by far better than I did!

1 Like
6

thank you very much @Steve-Mcl and @ralphwetzel. it was exactly what you mentioned.

best regards

7

This topic was automatically closed 14 days after the last reply. New replies are no longer allowed.