It will work but what we need is to record the data. I'm looking for a pre-owned Racepak Data Logger that I can pick up cheap. It has the capability for 100 samples per second and the types of channels needed for this little project.
One of these? I have it sitting in a box as it came out with my Siren Marine alarm upgrade. The new alarm has N2K built in so I have no use for this. If either of you want to play with it let me know and I will gladly ship it to you.
We can obtain data but the resolution for what we need won't be there. The challenge is to measure engine room air pressure and temperature over a very small range using pressure transducers with comparatively large ranges. Like Maretron I think these are 8 bit devices which will net very coarse "step function" data. We can always "smooth" the graph when displaying and overlaying data but now we are inventing data. If, for example you look at the Maretron DSM in graph mode on data like RPM you will see not a smooth transitioning graph but a series of steps as RPM goes up and down. The range of the RPM is broken up into segments corresponding upon the bit count of the device. For what we are trying to do that will not be data we can use. The second critical piece of this is the data rate - one or ten samples per second will not give us the resolution needed. We will need in the range of 100 samples per second minimum. Most affordable (less than 1BB) data loggers are 16 bit with averaging functions and sample rates between 10 and 100,000 SPS depending upon how large the memory is. Sample rate and number of channels are directly proportional to memory and recording time. There are a lot of old cheap but good data loggers out there but the software isn't included.....Thanks Grant, I have one for my EMU-1's, but perhaps Tom could get started with that.
Edit: Thats the MCT, did it come with the USB adapter cable?
But it would have the USB end on it -
The sensor other than the range of the sensor and using a current loop isn't the issue (up to the point to where external noise becomes the interfering factor). Those values are continuous and seamless. It is the acquisition of the data that is the issue. Let's say you have a 0 to 5 PSIG sensor and you are interested in 1 to 1.5 PSIG range. Acquiring that data is in digital segments obtained at a sample rate. If you have an 8-bit acquisition system then that range (0 to 5 psig) is divided into 8 segments or 0.625 psi per segment. Now as we are interested in 1 to 1.5 psig you only have around two steps for the entire range of interest. Software can smooth and interpolate but it is not enough data point resolution to get what we need. There are advanced features in some of the higher end DAS where a desired range of an instrument can be the totalized input and that range can be broken down into the resolution of the recorder.
The hypothesis is as engine load increases differential in air density between outside and in the engine room increases. This indicates and validates what some have stated as the engine room ventilation on some of our boats is inadequate. Consequently, the engine ECM's will dial back fuel and as a result power output will be below expectations.
Thanks @rlynch03 This is an important bulletin for anyone getting through the exhaust leak issues in the QSM high horsepower engines.
