Rheonics Support

This article covers the usage of the HART-specific commands available for Rheonics sensors. Only SRV

1. Command 128-Write SRV Density

This command is available in HART-7 (only), it accepts 6 Float values which are the Do0 to Do5(Coefficients from a temperature compensated density). 

Request Data Bytes

Response data bytes

Command specific response codes

Example: 

The Density SRV output can be described as a polynomial of the form: 

          (1)

This model can describe constant density or a temperature-dependent density.

a. Constant density input

To describe a constant density, the coefficient Do0 should be set equal to the constant density value, and all the other coefficients should be set to zero. 

b. Temperature-dependent density input

To describe a temperature-dependent density, assign values to the coefficients, that reflects the density behavior of your fluid with temperature. If you have a fluid reference table (for example Cannon fluids, Nippon grease), you can fit the density to a polynomial model to get the coefficients. 

All the tests below will be completed with HARTmpt software 

Command 128 - Write SRV Density

SRV HART devices can edit these coefficients by using the HART command 128, this can be achieved by using the coefficient in hex format.

1. Define the coefficient values based on a polynomial model, for example

2. Convert coefficients to Hex based on the request data bytes from the table 1 from section 1, all unused values must be covered too, otherwise, the command will return an error command

3. Input the hex value for all the coefficients 3F 80 00 00 3B 44 9B A6 3A 83 12 6F 00 00 00 00 00 00 00 00 00 00 00 00

4. Input data bytes with software like HARTmpt and click send command

Figure 1. Command 128, write density.

5. Command 128 response, the response is as expected based on Table 1

Figure 2. Command 128 response from HARTmpt.

2. Command 129-Read SRV density

This command is available in HART-7 (only), it accepts 6 Float values which are the Do0 to Do5(Coefficients from a temperature compensated density)

Request Data Bytes

Response data bytes

Command specific response codes

Command 129 will return the current values from the density model that are loaded into the SRV

Figure 3. Command 129 response.