SFM1 Heat Ratio Method Sap Flow Meter

The SFM1 Sap Flow Meter is a self-contained logging sensor ideal for field and laboratory measurement of plant water use. Storing plant water use data at a user defined frequency on an SD card, the sensor is suitable for measuring plant water use over extended periods. Data is stored in a CSV format and accessible via Combined Instrument Software (CIS). Optional external power from a 20-volt power supply or solar panel the SFM1 to be used for continuous sap flow monitoring.

The SFM1 Sap Flow Meter utilises the Heat Ratio Method (HRM) principle that is able to measure high, low and reverse flow rates in both small woody stems & roots as well as large trees (Burgess et al., 2001). Like the Heat Field Deformation (HFD) principle, the HRM SFM1 is the only instrument that can measure zero flow and reverse sap flow rates. If you are interested in remote access to data, please check out SFM1x – a member of ICT International’s family of IoT devices.

MEASUREMENT
Output Options	Raw Temperatures: °C Heat Pulse Velocity: cm hr-1 Sap Velocity: cm hr-1 Sap Flow: cm3 hr-1 (Litres hr-1)
Range	-100 to +100 cm hr-1
Resolution	0.01 cm hr-1
Accuracy	0.5 cm hr-1
Measurement Duration	120 seconds
Heat Pulse	User Adjustable: 20 Joules (default) approx. Equivalent to a 2.5 second heat pulse duration, auto scaling. User Adjustable: Minimum interval, 3 minutes, recommended minimum 10 minutes.

 

DATA
Computer Interface	USB
Data Storage	MicroSD Card

 

NEEDLE DESIGN
Needle Diameter	1.3 mm
Needle Length	35 mm
Measurement Positions	2 per measurement needle
Measurement Spacings	7.5 mm and 22.5 mm from the needle tip
Dimensions L x W X D	170 x 80 x 35 mm
Weight	400 g

 

POWER
Internal Battery Specifications
Battery	960mAh Lithium Polymer, 4.20 Volts fully charged
External Power Requirements
Bus Power	8-30 Volts DC, non-polarised, current draw is 190mA maximum at 17 volts per logger
USB Power	5 Volts DC
Internal Charge Rate
Bus Power	60mA – 200mA Variable internal charge rate, maximum charge rate of 200mA active when the external voltage rises above 16 Volts DC
USB Power	100mA fixed charge rate
Internal Power Management
Fully Charged Battery	4.20 Volts
Low Power Mode	3.60 Volts – Instrument ceases to take measurements
Discharged Battery	2.90 Volts – Instrument automatically switches off at and below this voltage when no external power connected.
Battery Life:	With a recommended power source connected, operation can be continuous. Approximately 1.5 days with a heat pulse of 50 Joules and a measurement interval of 30 minutes – no external power present to recharge battery.

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