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Notes for Tensiometer & Pressure Transducer Interfaces

ST1	Interface for GT3 Standard Tensiometer
Part No.	Description
	Range of Response:	0 to 100 kPa
	Output Display:	0 to 100 kPa
	Output Calibration:	Calibration for a 15 PSI Transducer at 4.2V
ST1-A	Interface (mV Output) for Vacuum Transducers with either 1 PSI, 15 PSI or 30 PSI range
	Range of Response:	-100 kPa to 200 kPa
	Output Display:	- or + mV in the range -50 mV to 100 mV Convention is negative for vacuum and no sign for positive pressure.
	Output Calibration:	The customer can connect a Vacuum Transducer of choice 1 PSI, 15 PSI or 30 PSI. The output in mV will not exceed the output display range of -50 mV to 100 mV at 4.2 V regulated power supply. The interface output in mV is linear and therefore a 2 point calibration (slope) only is required to convert mV to cm of water or kPa for either the 1 PSI, 15 PSI or 30 PSI Vacuum Transducers.
ST1-B	Interface (kPa Output) for Vacuum Transducers with either 1 PSI, 15 PSI or 30 PSI range
	Range of Response:	-100 kPa to 200 kPa
	Output Display:	kPa in the range -100 to 200 kPa Convention is negative for a vacuum and no sign for a positive pressure.
	Output Calibration:	Calibration for the respective 1 PSI, 15 PSI or 30 PSI at 4.2 V

Note: Customers must specify which pressure transducer type is to be connected to the ST1-B. A transducer specific calibration is required as the response of each of the 1 PSI, 15 PSI or 30 PSI Vacuum Transducers is different in sensitivity of PSI to mV. This correct calibration curve must be known to accurately convert the raw output to kPa.

System Resolution - General Notes

-100 kPa to 200 kPa is a maximum full scale range of 300 kPa.
Datalogger resolution is 16 bit or a full scale range divided by 65,000 parts.
A pressure of 100 kPa is equivalent to 1020 cm height column of water.
The full scale 300 kPa/65,000 = 0.00461 kPa/bit.
The equivalent resolution of the interface is = 0.47 mm H₂0.

Transducer Output - General Notes

Output for full scale at 10 volts:	0 - 1 PSI	is 16.7 mV
	0 - 15 PSI	is 0 - 100 mV
	0 - 30 PSI	is -50 - 100 mV

Output for full scale at 4.2 volts:	0 - 1 PSI	is 7.0 mV
	0 - 15 PSI	is 42 mV
	0 - 30 PSI	is 42 mV

Transducer Offset and Interface Autozero Function

Vacuum Transducers have an offset in them. This can be taken out by using the autozero function in the Smart Interface (ST1-A or ST1-B) in order to bring it back to zero.

Note: Calibrated units (i.e. those with kPa output [ST1-B]) must be used only with the specific transducer with which the electronics were calibrated. Failure to do so will result in an error that may be quite significant.

Links and Brochures
GT3-1 0 to -7 kPa Custom Tensiometer Transducers Download a printer-friendly version of GT3-1 Brochure (200K PDF)
GT3-15 0 to -100 kPa Jet fill Tensiometer Transducers Download a printer-friendly version of GT3-15 Brochure (200K PDF)
GT3-30 -100 to 200 kPa Jet fill Tensiometer Transducers Download a printer-friendly version of GT3-30 Brochure (200K PDF)
GT3-420 Jet fill Tensiometer Transducers Download a printer-friendly version of GT3-420 Brochure (200K PDF)
GT3 Custom Tensiometer Transducers
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