GUIDE FOR PURCHASING KART GAUGES
From analog products for beginners, to sophisticated digital instruments with a price of over 300 Euros: a very varied world in which to orientate yourself thanks to our report that analyses the main specific products for karting and explains what aspects should be evaluated before purchasing your next instrument for measuring tyre pressure
WHAT YOU NEED TO KNOW
Pressure gauges are divided into two types: analog and digital instruments. But before analysing both categories (and subsequently the main products on the market), let’s understand the reasons that oblige kart drivers to use pressure gauges.
When it comes to tyre working pressures, we enter a complex and broad universe in which theory and practical experience must be accompanied by measurement devices that are reliable and in line with the needs of those who bought them. In fact, an incorrect measurement of tyre pressure due to an insufficiently precise instrument, can completely compromise your performance driving a kart. The world of karts makes a lot more reference and is much more sensitive to tyre pressures than common road cars. Suffice it to say that the inflation pressure of a kart tyre is just over 0.5 bar, while in cars it is around 2 bar. This means that every slight variation, even of 1 tenth of a bar, has a considerable impact on tyre inflation pressure, in the karting field, less so in the automotive field. This obliges kart drivers to get pressure gauges for measuring the pressure every time before a new driving shift on the track.
And here begins … The confusion. In the sense that the pressure gauge market is hyper-structured and diversified, starting from the prices: ranging from 20-30 Euros, for basic items not specific for karting, up to 700 Euros, for the most complete ones in terms of their characteristics. However, before going into an analysis of products and their functionality, it is good to deal with the main classification, like most of the instruments for measuring physical phenomena, to which the gauges are subjected: analog instruments and digital instruments.
Car tyres and kart tyres: dimensions, but also totally different requirements regarding inflation pressures.
Analog devices transform the physical phenomenon of reference into a pulse for a meter. In the case of pressure gauges, the pressure data is provided by the measurement of the thrust, generated by the tyre air on the calibration rod along the scale in the dial.
However, given their mechanical nature these devices are more fragile and easier to adjust (often reaching full scale, for example). In this sense, it is important to take great care of these instruments and have protective devices capable of extending their life-cycles.
To further reduce the stress (often related to transport, conditions of use or the circumstances in which a pressure gauge is used) to which the mechanical components of analog pressure gauges are subjected, some manufacturers fill the pressure gauge with liquids (mainly glycerin solutions). If, on the one hand, this protects the internal mechanisms of pressure gauges, avoiding breakages or preventing the devices stopping, on the other hand it can, in particular atmospheric conditions or external pressure, lead to measurement variations even in the order of 2- 3 bars, which would prevent their use in the karting field. It is important in these cases to make sure that the selected pressure gauges have mechanisms capable of eliminating any environmental effect and allow the devices to always be reliable.
Analog devices are a good approach to pressures in karting, given the low costs as well as their ease of use and availability on the market.
When purchasing an analog pressure gauge, it is essential to find a good compromise between the size of the dial and the accuracy class of the device. In fact, for better readability and measurement accuracy it is important to have a generously sized dial: the larger it is, the lower the error percentage (i.e. the accuracy class) of the device.
Digital pressure gauges convert pressure into numerical data on a digital screen using a piezoresistive sensor.
This type of instrument is generally preferable to the analog type, both in relation to their accuracy (having on average a lower percentage of measurement error) and for the ease of reading the data that has been detected, since the univocal data on the display cannot be affected by a parallax error, that is influenced by the angle at which you look at the screen, as can happen in the case of the hand of an analog pressure gauge.
However, even for these devices there are mandatory aspects to consider. First of all, digital devices on average have a higher cost than analog devices: too low prices can mean less accurate and reliable sensors. They then need a power source, so they force you to keep this aspect under control. Basically, if you are a forgetful kart driver who goes karting once in a while and without being there to check the instruments available every time, perhaps an analog device, always ready for use, is more suitable. Finally, even digital devices are subject to the possibility of altering the setting. Most of the instruments, through the combined pressure of a few keys, can be reset manually and periodically. In one case, we will see, this function is instead available automatically, with a pressure gauge that automatically knows that it has been calibrated and applies an automatic reset.
The measurement range of the devices, especially with regard to analog pressure gauges, is of fundamental importance. In fact, these instruments are more precise and reliable when they work at the middle of the scale. What does that mean? Let’s take an example to better understand this: in karting, tyre inflation pressures oscillate approximately between 0.6 and 1.0 bar, depending on the compound and the track/environmental conditions. In light of this information, it would be ideal to have a pressure gauge that has these values in the middle of the dial scale, therefore a full scale at about 2.5 bar. This is because the accuracy of an analog gauge is at its highest in the second third of the gauge scale (between 25% and 75% of the full scale). If it is not possible to choose a pressure gauge that has a full scale that is approximately double the operating pressure, it is better to choose a pressure gauge with a range greater than double, rather than one with a range less than double.
The accuracy class of a device indicates the margin of error of the instrument in percentage terms with respect to the full scale value. In analog devices this is determined by the internal mechanical quality, the size of the dial and the full scale (the latter two measurements are closely related).
While for digital ones, the accuracy class is determined by the precision of the electronics and pressure sensor that is chosen by the manufacturer who will declare it when placing product on the market after tests. In both cases, the lower this value, the greater the accuracy in detecting the data by the device.
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