F-1
Appendix F. Dynagage Processing
Instruction (P67)
The Dynagage Processing instruction, Instruction 67, is used in conjunction with a Dynamax,
Inc. Dynagage stem flow gauge. Instruction 67 calculates the sap flow rate within a plant
stem by using an energy balance equation and inputs from a Dynagage sensor.
F.1 Function
Briefly, the energy input into the stem is a known quantity (Q
h
), and conductive
radial and vertical energy losses are calculated (Q
r
and Q
v
, respectively). The
residual energy is assumed lost through sap flow (Q
f
) and is given as:
Q
f
= Q
h
- (Q
r
+ Q
v
).
By measuring the change in temperature (dT) of the stem by heating and
assuming 4.186 Joules of energy are required to heat each gram of sap 1
°
C, the
flow rate can be calculated.
Accumulated flow can be calculated using datalogger Instruction 72 (Totalize).
F.2 Instruction Details
Dynagage Sap-Flow (P67)
1:
0000
Begin Input Location [ _________ ]
2:
0.0
K
sh
(W/mV)
3:
0.0
Heater Resistance(Ohm)
4:
0.0
Stem Area (sq cm)
5:
0.0
Thermal Conductivity (W/m
∗∗∗∗
K)
6:
0.0
Thermocouple Gap (cm)
7:
0.0
Low-Flow Cutoff Temperature (C)
8:
0.0
High-Flow Cutoff Velocity (cm/s)
9:
00
Output
10:
0000
Destination Input Location [ _________ ]
11:
0.0
Mult
12:
0.0
Offset
F.2.1 Input Voltages
Parameter 1
Four voltages must be stored sequentially beginning with the Input Loc option
stated in Parameter 1.
Input locations:
Loc 1: Ch (Thermopile (mV))
Loc 2: Ah (Upper TC (mV))
Loc 3: Bh (Lower TC (mV))
Loc 4: Voltage Input