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Data Analysis Fundamentals: Setting up a Data Logger

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Setting up a Data Logger

04.29

00:00 - It's all well and good having a good quality logging system in your car, however if you haven't got it configured correctly, then it's going to produce data that's largely meaningless.
00:10 This really is one of those cases where garbage in will result in garbage out.
00:15 Fortunately it's also not too difficult to get your logger configured and set up correctly so that you can rely on the data you're logging.
00:24 There are four main aspects that are important here, first we need to make sure that all of the sensors are calibrated and reading correctly so that we can trust the numbers they provide.
00:36 Secondly there are likely to be some sensors that need to be zeroed before heading out on track for your first session.
00:42 Steering angle, G force and damper position are just a few examples that come to mind here.
00:48 Next we need to make sure that the logger knows where the start/finish line is so that it can provide lap times.
00:56 Since this is a reasonably lengthly topic, we'll deal with it separately.
01:00 The last aspect we need to consider is data management.
01:03 You're going to be producing a lot of log files that can end up taking up a lot of memory and you need to organise them in a way that's easy to come back and reference at a later point.
01:15 There are two ways we can get data into our logger, either by directly connecting a sensor to it or by retrieving data from another device such as an ECU via a datastream or communications bus.
01:29 Both strategies require some care to make sure that the values we're logging are actually accurate.
01:36 Without getting into too much detail, a sensor is used to sample a physical condition such as a pressure, temperture or a position and then provide a signal to the logger or ECU in the form of a variable voltage.
01:51 Since the ECU or logger only sees the voltage it's up to us to tell it what that voltage means and this is done by assigning a calibration to that particular sensor.
02:02 In most cases, you'll be able to select from a range of common sensors, however you'll also have the ability to define a custom calibration table for unusual sensors.
02:13 In the case of the Honeywell sensor, the pressure is 0 psi at 0.5 volts and 150 psi at 4.5 volts.
02:22 You'll also want to assign the correct channel name to the sensor so that you know what you're looking at.
02:28 In this case, perhaps we're using the Honeywell sensor to monitor engine oil pressure.
02:33 It's a good practice to be consistent with your channel names so that you can overlay data from different cars and easily analyse the same piece of information.
02:42 For example, the oil pressure could be labelled oil pressure, engine oil pressure or maybe an abbreviation like oil pres.
02:51 Any of these will be just fine but just try to make sure you keep the naming convention consistent.
02:57 If you're receiving data from an aftermarket ECU or perhaps from the factory ECU via OBD2, then this can bring a new set of issues.
03:06 In this situation, the logger will usually receive scale data from the sensor rather than a raw voltage.
03:14 So this means that the sensor needs to be set up correctly inside your ECU.
03:18 You can also run into problems if the channel in the ECU is configured in imperial units and the logger is expecting metric units.
03:27 None of this is overly challenging and just requires a little common sense to check through each of your channels and make sure that you're actually receiving data that makes sense and is believable.
03:38 A good example of a sanity check is to check all your temperature channels before you start the car for the first time.
03:43 If the engine hasn't been running then you could reasonably expect that your air temperature, oil temperature and coolant temperature readings should all be within 1-2° of the ambient temperature.
03:55 As you visit more tracks in varying weather conditions, you're going to build up valuable historic data than can help get your car into the performance window and improve your lap times very quickly.
04:08 With this in mind, you need to be able to find the relevant data quickly and we certainly don't want any data to get lost.
04:15 For this reason it's important to make sure that you have a sensible strategy for managing your data.