The work described in the previous Liquid Level Measurement post has been stimulated by the shortcomings of existing (electrical) systems form measuring tank levels in a boat. Existing systems use potentiometers and floaters and these items have a short lifetime when living in a water, or diesel fuel or waste environment.
With the three EXT. channels of the DrDAQ plus the scope channel it is possible to monitor and record as many critical on-board parameters and to read all of them at the same time on the on board PC display. An important feature is that all critical parameters can be equipped with alarms. A big shortcoming of Picolog is the small size display of the quantities monitored, but this problem can be easily overcome by using EXCEL to interrogate the DrDAQ with a Macro.
Large parameter display
The original Macro for the Excel file has been written by Martin Berriman. I have modified it by adding a section to read the alarm status. The Excel file is enclosed and starts working as soon as it finds an active Picolog on the same PC.
Installation of the pneumatic liquid level measuring system requires some care. The pipe going from the "T" junction to the tank should start in a high place and then go down to the tank pipe, which should be at the lowest point of the system: this arrangement will avoid the rise of moisture in the pipe.
I am busy building the system panel. This meant removing the original instrument panel and building (mahogany) a new one (boat is Sweden Yachts C-41). The system will not use the DrAQ (inputs are scarce) but the Picolog 1000 and the PC will show (with alarms):
-Water tank level.
-Diesel tank level.
-12 V Utility battery voltage.
-Utility Alternator alarm.
-12 V Motor battery voltage.
-Motor Alternator alarm.
-Engine coolant temperature.
-Engine oil alarm.
-Engine RPM (I still have to test if Picolog will measure 50 Hz, corresponding to 3,000 RPM, but I am optimistic).
The PC also has Garmin cartography installed and uses the Garmin Bluetooth GPS MOBILE10 for navigation.
Will share all details after it is up and running.
Sorry, this now has become a Picolog 1000 design, after starting as a DrDAQ project.....However the system is now complete, tested and ready to be mounted in the boat. The display looks like this, only a few more alarms are to be added.
Large Excel display of all parameters
The front panel looks like this. The components to the left of the pumps control the battery charger and the alternators and do not concern the parameter display.
Metering panel, front
The general view of the metering module is shown below. Note the layout where care is taken in keeping the sensors in the topmost position.
Metering module, general view
The detail of the Metering module is self-explanatory and is shown below.
In the lab the RPM shown is obtained by taking a squarewave from the Function Generator of the DrDAQ driven by a separate PC. In actual service the RPM signal will be taken fro the "W" terminal of the alternator with a suitable resistor divider.
Amended Excel display
Module detail showing non-return valve support system