www.miinet.com
Moore Industries-International, Inc.
- 10 -
User’s Manual
238-760-00K
May 2019
Functional Safety Dual Input Smart HART® Temperature Transmitter
STZ
SECTION 1
Measurement Modes and Device Variables
The STZ can support one or two sensor inputs. With one input it provides an output which is
proportional to the input with options for trimming, custom linearization and scaling. With two
sensor inputs there are many other measurement modes:
Single Measurement
- Sensor 1 or Sensor 2 can be selected
Backup Measurement
- Sensor 1 fail to Sensor 2 or Sensor 2 fail to Sensor 1. If the primary
sensor fails the secondary sensor will continue to drive the analog output without any
interruption and a HART status flag is set.
Average Measurement
- This will output the average value of Sensor 1 and Sensor 2.
Differential Measurement
- Select from
-Differential: S1-S2
-Differential: S2-S1
-Absolute Differential: |S1-S2|
Low Select and High Select Measurements
- This will output the larger or smaller
measurement of Sensor 1 or Sensor 2.
For both single sensor and two sensor inputs there are many other variables, known as Device
Variables, that are calculated from the inputs. Most HART commands use variables known as
Dynamic Variables. The Device Variables need to be assigned or ‘mapped’ to the Dynamic
Variables.
The tables below define the Device Variables and Dynamic Variables.
Table 1.1.
Device Variables
Device Variable Description
Device
Variable
Use Sensor 2 until it fails then back up to Sensor 1
BU2-1
Use Sensor 1 until it fails then back up to Sensor 2
BU1-2
Reference Junction Compensation Temperature used for Thermocouple
compensation
RJC T
Sensor 1 reading ohms, mv, potentiometer, temperature with optional
trimming, scaling or custom curve applied
SEN1
Sensor 2 reading ohms, mv, potentiometer, temperature with optional
trimming, scaling or custom curve applied
SEN2
Calculate the average of Sensor 1 and Sensor 2
AVG
Sensor 1 minus Sensor 2
DIFF12
Sensor 2 minus Sensor 1
DIFF21
Absolute difference of Sensor 1 and Sensor 2
ABSDIF
Selects the lower (smaller) of Sensor 1 and Sensor 2
LOSEL
Selects the higher (larger) of Sensor 1 and Sensor 2
HISEL
Device
Variable
Code
0
1
2
3
4
5
6
7
8
9
10
11
12
--
--
Reserved for MII
Reserved for MII