Pressure and weighing sensors are generally supplied as a 350Ω strain gauge bridge device, requiring a regulated excitation supply and outputting a millivolt signal, or a 2-wire transmitter which requires a 24VDC supply and outputs a 4-20mA signal.
The following instruments can power and measure both these sensor types:
- Tracker 210 Low Cost 4-Digit Indicator
- Tracker 212 Low Cost 5-Digit with 4-20mA signal linearisation
- Tracker 220 Series - High accuracy 4/5-Digit + RS485
- Tracker 250 5-Digit Melt Pressure - Auto Calibration resistor switching + RS485
- Tracker 321 and 332 (PID) DIN Rail modules + RS485
For multiple load cells (multiple strain gauge bridges):
- Tracker 240 5-Digit Load Cell Indicator + RS485
All the products listed above have the following as standard or can be fitted as an option:
- Isolated Analogue Output
- Alarm Relays
- Zero Function
- Tare Function
- Max / Min Memory + Reset
- User Calibration Function (see below)
Using the user calibration feature, the Tracker and sensor can be match calibrated together where the instrument measuresand stores the sensors signal at two or more pressures or weights. This greatly reduces errors due to sensor output and excitation supply voltage variations. The displayed values can be in any engineering units.
On the 200 series a front panel button, or status (logic) inputs on some models, can be configured to provide an auto zero feature allowing zero offset errors to be eliminated. For weighing applications, a tare function can be similarly configured.
For zero and tare functions on a T300 command must be sent via the RS485 interface or remote switches connected to the status inputs on the T340 logic expansion module.