Bimetallic thermometer verification regulation encountered in the execution of a problem

ROb magnetic flap | | glass thermometer thermometer floating ball | | glass thermometer thermometer two-color thermometer

JJG 226 - 2001 the bimetallic thermometer verification regulations, requirements for calibration of error is: the verification of the thermometer should be the two stroke in positive, point by point in the direction of the upper or lower limit, respectively. Only when measuring upper and lower limit for single trip test.

the author thinks that the requirements in the practical work is not very reasonable. Because domestic verification 0 ~ 300 ℃ in the scope of all kinds of thermometer of the equipment configuration by oil is usually constant temperature 90 ℃ ~ 300 ℃, the constant temperature water trough at room temperature to 100 ℃, constant temperature trough - alcohol 50℃ ~ 50℃ 。 Which a few kinds equipment only in constant temperature trough can in - alcohol 50 ℃ ~ 50 ℃ within the scope of control of heating and cooling. And constant temperature tank and the thermostatic water tank can control heating, cooling can only rely on natural cooling.

in the existing circumstances, when the test thermometer return ( From high to low temperatures) Will encounter problems. Because

tank and water tank cooling from high temperature to low temperature for a long time, often need a few to 10 h. Such as oil temperature to 250 ℃ and then cooled to 100 ℃ needs more than 7 ~ 8 h. This gives the verification caused great difficulties.

if the electric contact bimetallic thermometer is more trouble, because when the test was carried out on the set point, need to slowly change the thermostatic bath temperature, a little bit slowly find switching value. Due to large bimetallic thermometer error, so would be very slow to find, let alone test is positive, the trip, the trip or natural cooling. Due to the above problems, the author thinks that under the condition of the domestic existing, fully in accordance with current regulations verification is difficult, can consider reducing hysterisis error check point. For example, 0 ~ 120) ℃ when the bimetallic thermometer calibration only 40 ℃ hysterisis error, so it can be in the tank test after 100 ℃, immediately put thermometer has constant temperature in the tank test of 40 ℃, save a lot of time. For electric contact bimetallic thermometer calibration, would you please consider constant temperature trough constant in a certain temperature, the temperature is constant in a certain standard thermometer set needle after adjustment, make slowly close to the instructions set needle, closing and opening of the switching action until the contact. Instant record set pointer value in the movement, and then by calculating the average of up and down stroke set pointer value and standard value as the difference between the set point value for error.

by the above method can guarantee the quality of work under the existing conditions and improves the work efficiency.