Transmitter how to distinguish good or bad1

Instrument manufacturer is now a variety of, a lot of instruments is illusory. It's the same in the transmitter, the transmitter brands on the market is very much, the stand or fall of transmitter is also difficult to identify. So what is the distinguish method allows users to buy when buy good transmitter, the project is to introduce how to discern the stand or fall of transmitter.

1, the benchmark to stability, 4 ma is corresponding to the input zero benchmark, the benchmark instability, talk about any linearity, precision cold boot 4 ma within three minutes of zero drift changes within no more than 4000 ma05 %; （ That is, 398 - 402mA） And the pressure drop in load 250 Ω is 0995 v - 1005 v, foreign IC heart more expensive energy gap benchmark, temperature drift coefficient of 10 PPM per degree of change;

2, internal circuit current total consumption & lt; ； 4 ma, plus after setting is 4000 ma, let it flow and active rectifier filter circuit does not change because the original edge input consumption current changes, foreign IC heart using constant current power supply;

3, when the working voltage 24000 v, 20000 ma, full scale full scale readings by load on a scale of 0-20000 ma 700 Ω vary; Change within no more than 20000 ma05 %;

4, when the full scale 20000 ma, load 250 Ω, full scale 20000 ma readings by working voltage 15000 v - 30000 v, Change within no more than 20000 ma05 %;

5, when the original edge of overload, the output current is not more than 25000 ma, + 10%, otherwise PLCDCS work 24 v power supply for transmitter and AD input clamp circuit damage due to excessive power consumption, another shot with the output of transmitter inside also damage due to excessive power consumption, no more suffer AD input clamp circuit;

6, when the work voltage 24 v is allowed to damage when the transmitter, must have the polarity protection;

7, when the two line between induction thunder and induced surge voltage exceeds 24 v to clamp, shall not damage the transmitter; General parallel 1 - between two lines Two TVS transient protection diode; 15 ke inhibits once every 20 seconds interval of 20 milliseconds pulse width of the impact of the positive and negative pulse, the transient impact under power 15 kw - 3千瓦;

8, the original input overload must be current limit: the original edge input overload is greater than 125% when the output flow limit 25 ma + 10% ( 2500 - 2750mA） The load on the 250 Ω pressure drop is 6250 - 6875V；

9, there is no more than 24 v induction surge voltage clamping discrimination: in two line output port and a ac 50 v pointer meter, used to connect two wires to ac 50 v instant touch two line output port, the presence of clamp, clamp how many volts can be clear at a glance,

10, to identify the presence of polarity protection: use pointer multimeter Ω by 10 k file and measure two line output port, there is always a Ω resistance value is infinite, there is polarity protection;

11, there are infinite output current for a long time short circuit protection: the original edge input or overload is more than 125% - 100% 200%, will load 250 Ω short circuit, measuring whether the short circuit protection in 25 ma + 10%;

12, to identify the level of industrial and civil commercial level, industry level working temperature range is - 25 degrees to + 70 degrees, 100 parts per million per degree of temperature drift coefficient is change, namely 1 degree per degree of temperature change, the accuracy of change to one over ten thousand; Level of civil commercial operating temperature range is 0 ( Or - 10 degrees) To + 70 degrees ( Or + 50 degrees) , per degree of temperature drift coefficient is 250 PPM, namely 1 degree per degree of temperature change, the accuracy of change than per two point five; The temperature drift coefficient of current voltage transducer can use constant temperature box or high and low temperature box to test was complicated.

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key words: thermal resistance, thermocouple, thermal resistance, platinum resistance, PT100, PT1000, pressure sensor and digital temperature sensor