For HART communication, Rheonics provides the following variables (PV, SV, TV, and QV) over Channel 1 analog output 4-20mA.
| Primary Variable (PV) | Density | g/cc |
| Secondary Variable (SV) | Viscosity | cP |
| Tertiary Variable (TV) | Temperature | °C |
Quaternary Variable (QV) | Sensor Status |
Table 1. HART variables.
1. Primary VariableThe primary Variable is always defined by what is currently set in Channel 1 with the RCP software
2. Secondary Variable and Tertiary VariableThose variables have to be ordered and configured before delivering the sensor, the following table contains the available parameters to be set as Secondary Variable and Tertiary Variable.
Table 2. Parameter Table
3. Quaternary Variable - Sensor StatusAll Rheonics sensors (SRV, SRD, DVP, DVM) for inline viscosity and density monitoring have inbuilt status. Sensor status is always available as the fourth variable
The sensor status can take any of the following values:
Bit | Hex | Name | Comment |
Bit 0 | 0x0001 | PLL frequency mismatch | The PLL frequency does not match the sensor frequency. Derived from the ASB string (E10) |
Bit 1 | 0x0002 | PLL not locked | The PLL is not locked. Derived from the ASB string (E01) |
Bit 2 | 0x0004 | PLL lock incorrect | The PLL has locked on a wrong frequency. Derived from the ASB string (E02) |
Bit 3 | 0x0008 | ASB communication error | Issues with sensor electronics |
Bit 4 | 0x0010 | Temperature sensor failed | The temperature sensor has failed. Derived from the ASB string if the temperature is -273.0 |
Bit 5 | 0x0020 | Sensor too hot | If the temperature is above the hardcoded physical temperature limit. |
Bit 6 | 0x0040 | ASB communication error | Communication issue between two electronics board in the SME |
Bit 7 | 0x0080 | Serial Changed |
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Bit 8 | 0x0100 | Status not clean | Sensor is not clean (only SRV) |
Bit 9 | 0x0200 | Status in Air | Determines if sensor is in air |
Bit 10 -15 | Unused |
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Table 3. Sensor error status bit code and description.
How to read sensor status?
Sensor status is a WORD data type, these status bits can be used over digital communication channels to understand when the sensor is operating correctly and when there is an issue.
Sensor error status is the combination of any bit, in this scenario Error 512 is the combination (OR) of the error bits also this decimal value should be converted to its hexadecimal representation, which is “200”, A sensor error status with code 200 means that the sensor is in air.
4. Default configuration for Rheonics Sensor| SRV Default configuration | |
| PV | Viscosity |
| SV | Density |
| TV | Temperature |
| QV | Sensor Status |
| SRD Default configuration | |
| PV | Density |
| SV | Viscosity |
| TV | Temperature |
| QV | Sensor Status |
References: