Reading Current Scaler Values¶

Document Context¶

Purpose: API for reading current scaler values applied to DLMS meter registers using OBIS codes for data scaling and unit conversion
When to use: Understanding meter data scaling, troubleshooting value discrepancies, verifying COSEM Class 3 object scaling
Prerequisites: DLMS meter communication, OBIS code knowledge, understanding of COSEM Class 3 objects and power-of-ten scaling
Related to: Custom scalers, Meter communication, data reporting endpoints
Validates against: DLMS/COSEM standards, OBIS code specifications, meter scaling behavior in COSEM Class 3

Key Facts¶

Endpoint: /api/v1/meter/scalers/current - Reads current scaling factors for OBIS codes
Method: GET - Returns JSON array of OBIS codes with their active scalers
Compatibility: DLMS meters only, COSEM Class 3 objects, available since firmware 1.2.15
Scaling: Power-of-ten multipliers (-3 to +3 typical range)
OBIS format: Shortened C.D.E notation for recognized meter registers

Authentication

When a Web UI password is set, HTTP endpoints require HTTP authentication.

Firmware 1.10.X and later: Uses HTTP Digest authentication - Server challenges with WWW-Authenticate: Digest … (realm is the device hostname) - Algorithm: MD5-sess (device advertises MD5-sess; integrity variant supported) - qop: auth (and optionally auth-int for requests with body integrity) - Nonce and opaque are issued by the device; the client must include cnonce and increment nc - Expired nonce: server may return 401 with WWW-Authenticate: …, stale=true. In that case, retry the same request once using the new server challenge, a new cnonce, and reset nc=00000001.

Firmware before 1.10.X: Uses HTTP Basic authentication - Server challenges with WWW-Authenticate: Basic realm="..." - Credentials are base64-encoded in Authorization: Basic <encoded-credentials>

Recommended approach: Use --anyauth in curl to automatically detect and use the appropriate method:

curl --anyauth -u ":<password>" http://whatwatt-ABCDEF.local/api/v1/system

DLMS Only

Currently, reading current scaler values is only available for meters that exchange data in DLMS format.

COSEM Class 3

Scale factors apply only to COSEM Class 3 objects.

How Scalers Work¶

The present value is the value that has been determined by the device itself at the detection stage, covered/overridden by a set of scalers selected by the scalers_set (note that the scalers_set does not have to cover all values).

Endpoint Details¶

This endpoint allows you to read individual scale values for specific register values that the meter transmits. This API uses a shortened convention of logical name/OBIS, which is in the format C.D.E.

Parameter	Value
Endpoint	`/api/v1/meter/scalers/current`
Method	`GET`
Response Content Type	`application/json`
Available Since	Firmware version 1.2.15

Response Format¶

The endpoint returns an array of OBIS codes with their current scaler values.

Response Fields¶

Field	Type	Description
`obis`	string	Shorthand representation of the OBIS notation (C.D.E format). Only OBIS codes recognized by the device and belonging to COSEM class 3 are included
`scaler`	int	Currently applied scaling factor expressed as power of ten (10^scaler)

Scaler Value Interpretation¶

Scaler Value	Multiplier	Effect	Example
`-3`	0.001	Divide by 1000	1000 → 1.0
`-2`	0.01	Divide by 100	150 → 1.50
`-1`	0.1	Divide by 10	25 → 2.5
`0`	1	No scaling	100 → 100
`1`	10	Multiply by 10	5 → 50
`2`	100	Multiply by 100	3 → 300
`3`	1000	Multiply by 1000	2 → 2000

Example Request¶

curl -s http://192.168.1.100/api/v1/meter/scalers/current

Example Response¶

[
  {
    "obis": "1.8.0",
    "scaler": 0
  },
  {
    "obis": "2.8.0",
    "scaler": 0
  },
  {
    "obis": "3.8.0",
    "scaler": 0
  },
  {
    "obis": "4.8.0",
    "scaler": 0
  },
  {
    "obis": "1.7.0",
    "scaler": 0
  },
  {
    "obis": "2.7.0",
    "scaler": 0
  },
  {
    "obis": "32.7.0",
    "scaler": 0
  },
  {
    "obis": "52.7.0",
    "scaler": 0
  },
  {
    "obis": "72.7.0",
    "scaler": 0
  },
  {
    "obis": "31.7.0",
    "scaler": -2
  },
  {
    "obis": "51.7.0",
    "scaler": -2
  },
  {
    "obis": "71.7.0",
    "scaler": -2
  }
]

Common OBIS Codes¶

Energy Values (typically scaler: 0)¶

1.8.0 - Positive active energy total
2.8.0 - Negative active energy total
3.8.0 - Positive reactive energy total
4.8.0 - Negative reactive energy total

Power Values (typically scaler: 0)¶

1.7.0 - Positive active instantaneous power
2.7.0 - Negative active instantaneous power

Voltage Values (typically scaler: 0)¶

32.7.0 - Voltage L1
52.7.0 - Voltage L2
72.7.0 - Voltage L3

Current Values (typically scaler: -2)¶

31.7.0 - Current L1 (often scaled by 0.01)
51.7.0 - Current L2 (often scaled by 0.01)
71.7.0 - Current L3 (often scaled by 0.01)

Use this endpoint to understand how raw meter values are being scaled before they appear in the final report data.