If any 5 results exceed the tolerance, the test conditions and operating techniques should be carefully checked and the existing temperature corrected before recalibrating, discarding all existing results.

Evaluation methods for accuracy

Evaluate with standard samples, using two or more standard samples twice each, with a range of no more than 120J/g. If the difference between the average value and the standard value is within the range of uncertainty, the accuracy is considered qualified, otherwise it is unqualified.

Evaluate with benzoic acid, perform two calorific value measurements with 0.7g and 1.3g of benzoic acid each. If the difference between the average calorific value of each mass and the standard value of benzoic acid is not greater than 60J/g, the accuracy is considered qualified, otherwise it is unqualified.

What are the main reasons for inaccurate calorific value measurement results?

Inaccurate calibration of heat capacity often leads to system errors, which are generally caused by the use of unqualified benzoic acid, forgetting to add nitric acid to form heat when calculating heat capacity, or the inconsistency between the water volume in the inner cylinder and the calibration time of heat capacity during heat generation measurement;

Poor contact in the wiring part of the agitator, jamming of the mixing blade, or uneven mixing speed generally manifests as high or low results in repeated measurements of heat capacity or heat generation. The difference is far.

The water volume in the inner cylinder cannot be consistent. If the water volume in the inner cylinder changes by 5g, the instrument's heat capacity will change by 21J/K. For a temperature rise of 3K, the resulting heat generation error is about 63J.

The performance of an automatic calorimeter is not very stable, such as temperature fluctuations. Therefore, the instrument should often use praise or standard benzoic acid as a price difference. Standard substances or changes in benzoic acid quality can be used for quality inspection, but the same mass of benzoic acid cannot be used for reverse calibration alone.