本篇着眼于在塑料挤出和注塑应用中的高温熔体压力传感器。从传感器中输出的信号需要由仪表校准。确保压力测量的精度和稳定。
在进行校准操作前，一是传感器停止工作，二是操作温度内，三是温度补偿调至零。
所有单尼斯科传感器有温度补偿等级，其选择依据是传感器中毛细管中填充介质。填充介质的物理属性与零度输出等级有直接关联。当用仪表分配量程时，需要考虑这个值，并作出调整以补偿。校准调整的作用类似于设置天平，可以将温度补偿想象成所称物品的包装。
3种不同介质的温度补偿如下：
• hg（汞）= 15 psi/ 100°f or 27 psi/ 100°c
• oil（油）= 36 psi/ 100°f or 65psi/100°c
• nak（钠钾）= 30 psi/ 100°f or 54psi/ 100°c
举例：
过程温度 = 200 oc, 汞填充，信号输出60psi @零点压力
①根据传感器的全量程压力范围，这个偏移量在常规组合误差规范外。压力范围是10,000 psi，综合误差是0.5%，补偿实际上是110psi。②谨记当我们执行校准时，对信号输出没有任何变化，只有确保输出在规范的容差范围内。③dynisco仪表的设计易于过程校准，仅需几个案件即可测试输出的高/低界限范围。
our topic focuses on the melt pressure transducer, that is used in plasticextrusion and injection molding. the signal output from the sensor should becalibrated with instrumentation. this is considered vital to the accuracy andreliability of the pressure measurement.
proper calibration should be performed with the transducer at rest (nopressure applied) and at operating temperature, to compensate for temperatureeffect on zero.
all dynisco pressure transducers include a rating of temperature effect onzero, and this rating can change depending on the selected fill media in thetransducer capillary.
physical properties of the liquid fill media, will effect where the zerooutput level of the signal will be, and this value needs to be considered whenassigning the range with instrumentation, and adjustments would be made tocompensate.
this adjustment would be similar to setting a tare on a balance, where thetemperature effect is equivalent of the package of the product you are weighing.
the published temperature effect for the 3 liquid fill options are as follows:
based on these values we expect that the instrument will need to beconfigured to accept the signal input as zero, by performing calibration at theoperating temperature of the process.
example:
processtemperature = 400°f, hg typesensor showing signal output of 60 psi @ zero pressure*
*depending on the full scale pressure range of the transducer, this offset would be in addition to our normal combined error specification, so a10,000 psi range that has a .5% combined error ( /- 50 psi) would actual appearto have an offset of 110psi or more at any time.
it is important to remember, that when we are performingcalibration, there are no changes being made to the signal output, onlyverification that output is still within tolerance, of the modelspecifications.
dynisco instruments are designed to make calibration of pressure sensorsan easy process. our indicators and controllers can test the high and low limitof the signal output with a few key strokes.
