What is the required temperature difference between the air prover oil and the meter under test when using a bell prover?

The requirement for the temperature difference between the air prover oil and the meter under test when using a bell prover is critical to ensuring accurate measurements. When the temperatures of both are within 1 degree of each other, it helps to minimize the effects of thermal expansion and contraction on the fluid measurements. This close temperature alignment ensures that the density of the oil remains consistent, which directly impacts the volume calculations during the measurement process.

If the temperatures diverge significantly, it could result in variations in density that lead to inaccuracies in the flow measurement. By maintaining a temperature difference of no more than 1 degree, the accuracy of the prover's readings is upheld, which is essential for reliable measurement verification in the context of custody transfer or calibration standards.