Resistance & Temperature Measurement from Cropico
There are several reasons why the resistance of material needs to be measured in the automotive industry, particularly measuring the resistance of electrically powered equipment like robot welding cables to ensure the weld quality does not deteriorate.
Others include the measurement of battery lead crimp connectors, the resistance of air bag detonator, resistance of wiring harnesses and the quality of crimp connectors on components.
The ability to make accurate and reliable measurements is therefore crucial but, with the values involved usually very low - often down to milliohms - the key requirement is to understand and eliminate potential sources of error from the measurement process.
To achieve this Cropico, the specialist supplier of precision measurement equipment, offers a range of advanced, precision instruments capable of meeting the demanding requirements of the automotive production environment.
The Cropico Series 4000 digital ohmmeter range provides a practical solution for a wide range of low resistance measurement applications.
The portable and rugged instrument includes a number of advanced features to ensure measurement accuracy including forward and reverse current measurement with auto averaging, true current zero, long scale length and a selectable measurement range from 40mohms to 4k ohm with respective resolutions between 10m ohm and 1ohm.
Showing posts with label temperature measurement. Show all posts
Showing posts with label temperature measurement. Show all posts
Friday, 30 July 2010
Thursday, 15 July 2010
Temperature Measurement - Processes
Temperature affects all processes but it’s always difficult to measure. Here, Bill Earlie of electrical test and measurement specialists Cropico looks at one way of achieving greater accuracy in temperature measurement - platinum resistance thermometers.
Platinum resistance thermometers are much more accurate than thermocouples but they have some drawbacks, notably a more limited temperature range, a higher thermal mass and usually are more expensive. These resistance thermometers have a linear and repeatable resistance against temperature: The two common types in use are Pt100 which has a resistance of 100Ω at 0°C and Pt25 which has a resistance of 25Ω at 0°C.
Platinum is used because it has a stable temperature coefficient and being a noble metal is not very susceptible to contamination. Pt100 (PRT) is the most commonly used and has a temperature coefficient of ? = 0.00385 (European standard) which corresponds to an average resistance change, over the temperature range 0 to 100°C of 0.385Ω per °C.
Both the absolute resistance value and the change in resistance per °C are both relatively small and give rise to measurement problems, especially when the resistance of the connection leads are taken into consideration. There are other standards also in use – for instance, the US standard for pt100 has an alpha of 0.00392.
Platinum resistance thermometers are much more accurate than thermocouples but they have some drawbacks, notably a more limited temperature range, a higher thermal mass and usually are more expensive. These resistance thermometers have a linear and repeatable resistance against temperature: The two common types in use are Pt100 which has a resistance of 100Ω at 0°C and Pt25 which has a resistance of 25Ω at 0°C.
Platinum is used because it has a stable temperature coefficient and being a noble metal is not very susceptible to contamination. Pt100 (PRT) is the most commonly used and has a temperature coefficient of ? = 0.00385 (European standard) which corresponds to an average resistance change, over the temperature range 0 to 100°C of 0.385Ω per °C.
Both the absolute resistance value and the change in resistance per °C are both relatively small and give rise to measurement problems, especially when the resistance of the connection leads are taken into consideration. There are other standards also in use – for instance, the US standard for pt100 has an alpha of 0.00392.
Thursday, 8 July 2010
Temperature Scales
There are three temperature scales in use today.
These are used for temperature measurement.
The Celsius scale, the Kelvin scale & the Fahrenheit scale. A comparison of the three can be found below:
These are used for temperature measurement.
The Celsius scale, the Kelvin scale & the Fahrenheit scale. A comparison of the three can be found below:
Tuesday, 6 July 2010
What is Temperature?
Temperature can be defined as the amount of hotness or coldness of a body or environment.
It can, however, be more accurately described as molecular motion and energy flow, and can be measure in a number of ways ie. the expansion of a liquid as seen in liquid in glass thermometers, or the change in resistance of a material such as copper or platinum.
Cropico are world leaders in accurate temperature measurement.
Heat
Heat is internal energy that flows from a system at a higher temperature to a system at a lower temperature. Two bodies at the same temperature are said to be in thermal equilibrium.
If a body at a higher temperature comes into contact with a body at lower temperature, heat will flow from the higher temperature to the lower one. If an ice cube is placed in a warm drink the heat from the drink will flow into the ice cube and melt it. The ice cube does not transfer its coldness to the drink, but of course the overall effect is for the drink to become slightly cooler.
It can, however, be more accurately described as molecular motion and energy flow, and can be measure in a number of ways ie. the expansion of a liquid as seen in liquid in glass thermometers, or the change in resistance of a material such as copper or platinum.
Cropico are world leaders in accurate temperature measurement.
Heat
Heat is internal energy that flows from a system at a higher temperature to a system at a lower temperature. Two bodies at the same temperature are said to be in thermal equilibrium.
If a body at a higher temperature comes into contact with a body at lower temperature, heat will flow from the higher temperature to the lower one. If an ice cube is placed in a warm drink the heat from the drink will flow into the ice cube and melt it. The ice cube does not transfer its coldness to the drink, but of course the overall effect is for the drink to become slightly cooler.
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