The precision of the thermocouple sensor in daily measurement need to be controlled

I need a PID or ON/OFF control?

in general, if your system from the heat source (fast From the change of heater power to observe the temperature change of the load) Move the heat to the controlled area or available heat, matches or exceeds the quantity of heat that use up less than than a factor of about 2, the ON/OFF control will give better performance. That is to say, ON/OFF control will generate less than PID control overshoot, faster and smaller deviation of preheating, without the need for a lot of adjustments.

if there is a long delay, the change between the heater power and the temperature of the load produced many seconds or minutes, or if the heater power over load demand is about 2 times or more, the PID control.

indicates the difference between the temperature control accuracy and precision?

the precision of temperature control specification means that you can read the temperature on the display, or dial in value. 102. 3 c shows accurate to 0. 3 degrees and 123 degrees show that only accurate to 1 degree.

means that it will and readings of the temperature control precision by the calibration and dates back to the international standard thermometer readings for the same, and measure the same point.

I can control my system to 1/100?

trying to design a temperature control system, hold the load at 1/100 degrees ( F or C) , even before the 1/10 certain temperature, it is important to consider in a typical material and temperature of reaction.

the temperature of the load always response to add or remove heat. When the heat flow through any solid, gas or liquid, according to its thermal properties to change the temperature of the material. Usually, after the system is stable, dominate the nature is the thermal conductivity.

although can control a specific, small load area, such as 1/100 degrees, but may find heat flow in and out of the area will reduce the control of the area around the coefficient of thermal conductivity. This has nothing to do with the performance of the control; It is the result of the physics of heat flow.

for example, through the 6 & times; 6 inches of aluminum can produce as much as 10 watts per inch degrees Fahrenheit 1/8 gradient, even if the location of the thermocouple is control the insert to the exact temperature.

if required by the load change the heat flow, even a little bit, in one place, The thermocouple location) The precise temperature control may be significantly reduced in the area. Therefore, in the actual system load on a lot of impossible for such as 1/100 degrees of accuracy control.

why I read in my system is different from the temperature control of the performance of the value of the thermometer?

used to check the temperature control performance of any thermometer, thermocouple must be placed in and connected to the temperature control is exactly the same point. Two thermocouples should actually come into contact with each other.

point to point controlled system of temperature gradient, whether solid, liquid or gas, can be more degrees. Unless two thermocouple used to check each other's actually in the same, or more will be the most unreliable, and in the worst case is meaningless.

how to get my system to achieve temperature faster?

fast start, low overshoot and simple ( Low cost) Temperature control is almost a mutually exclusive demands. Simply to increase the heater power to exceed that required by the load in the balance of power will result in faster startup, but it will also be during operation produce big overshoot and oscillation of more around the set point.

to adjust the size of the heater is slightly larger than the biggest load balancing requirements, and the location of the thermocouple location in as close as possible to load, is always good for optimal design method of temperature control.

if you need quick start, you must make everything possible to reduce the load of heat storage, and thermocouple and heaters are tightly coupled to the load. Then can increase the heater power more than balance the load requirements, but will need special design in the temperature control to reduce the overshoot of the trend.

why I open the system occurs so much overshoot?

heat need time from the source ( For example the resistance heating element) Load or controlled area flow into the system. When the system is open, hot & other; Package & throughout; Begin to spread into the system and, until it reaches the control system of thermocouple. Even control the fully closed heat, enough calories will start marching toward the thermocouple, the temperature will continue to increase. Overshoot will depend on the degree of heater and load capacity and system dissipation ratio. If heater can pass than system used or dissipate more heat, heat the overshoot can be quite large.

unless specifically designed for temperature control by opening or slow & other; Throughout stage &; To deal with this kind of situation, otherwise nothing can eliminate the overshoot is started. When the heater is stronger than needed for the load power, quick start and little or no overshoot will be particularly difficult to achieve.

the relevant recommendation: wear-resistant thermocouple;