54
SeCtion b
SoFtware Manual
RetuRn to toC
MaCe HydRoMaCe 3000
Product Manual
55
RetuRn to toC
Offset adjust
This function is used to “fine tune” the depth reading whenever the sensor
is deployed or reading inaccurately. For example, the depth sensor may
be sitting slightly off the bottom of the stream, or the user has deployed it
above a silt line on the side of a pipe.
WarNINg: When calibrating a depth channel, measurements should
aLWaYS be carried out from the BOttOM of the channel/pipe to the top
of the water level
1.
Click
“Offset adjust”
from the
“Edit channel”
dialogue box and the
“Channel
offset adjust”
dialogue box appears.
The
“Current value”
from the sensor (in this case a
depth sensor with frequency output) is displayed
at the top of the window and is updated
approximately once per second.
2.
To adjust the
“Current value”
, enter your current measured value in the
“Corrected value”
field.
3.
Click on the
“Apply”
button to calculate the new
“Offset”
parameter value
for the associated channel. Clicking on the
“Cancel”
button terminates the
procedure without altering the offset value.
21.3.1 Edit “Depth” channel type
- continued
Channel path
This describes the channel type and the module input source.
Channel name
This is the name given to the channel by the user when setup.
NOte: this name will also show on the hM 3000 LCD screen if the
Display channel check box is ticked
Decimal places
The user can set the number of decimal places (0, 1, 2, 3) using the drop down list
box. These decimal places will be shown in both the data file and the LCD.
Display channel
If this check box is ticked then this channel will be displayed on the HM 3000 LCD.
Log channel
If this check box is ticked then this channel will be logged in the data file.
Units
This sets the units on the logged value. This is a text field and is user defined.
NOte: If a “Velocity” or “Depth” channel type is configured on a
“4-20ma” input the units are defined according to the “System
settings”
Value at 4ma
Enter the value here that corresponds to an input of 4mA.
Value at 20ma
Enter the value here that corresponds to an input of 20mA.
21.3.2 Edit “4-20mA” input type
-
I/O card
Channel path
Display channel
Channel name
Log channel
Decimal places
Units
Value at 4mA
Value at 20mA
Manually calculating slope and offset values
Slope = Sensor range ÷ Span
Offset = - (Slope x Sensor output at zero)
Sensor Range:
The measuring range of the sensor. For example a depth
sensor may be ranged from 0 to 2m.
Span:
Is the difference between the sensor output (Frequency or Voltage) at
the top of the measured range (say 2m) and the sensor output at zero.
For example, you wish to calculate the slope and offset for an ultrasonic
depth sensor that has a range of 0 to 1250mm. At 0mm the sensor outputs a
frequency of 100Hz and at 1250mm the sensor outputs 2500Hz.
The following calculations will provide the sensor’s slope and offset:
Slope = 1250 ÷ (2500-100)
Offset = - (0.5208 x 100)
= 1250 ÷ (2400)
= - 52.08
= 0.5208
