0
In a current loop, 4-20 ma is a typical range. We don't use 0 ma as a valid signal, because that is reserved for a broken wire or dead transmitter condition. The receiver is designed to offset and translate the 4-20 as necessary, with the break condition also being reported.
Wiki User
∙ 12y ago
Add your answer:
Earn +20 pts
What is the current in a 100 ohm resistor connected to a 0.40 volt source of potential difference?
V=RI or I = V/R so I = 0.4/100=0.004A or 4mA
Definition of 4-20 mA?
Previously when transmitters were configured for 0-20mA signal it was very difficult to identify an open circuit at 0mA,hence to supersede this defect it was decided to configure the transmitter as 4-20mA signal,so that if there is open signal it can be easily identified.
What is analog transmitter?
a device used to convert a process measurement (i.e. temp, pressure, level) to an analog value which is typically 4-20 mA of electrical current. For instance you need to measure the temperature of water in a pipe. An RTD or a thermocouple will be attached in a way that it can sense the temp. The transmitter will read the temp from which ever you use and convert it into milliamps. So if the range of the transmitter is 0-100 degrees F at 0 degrees the transmitter will output 4mA at 100 degrees it will output 20mA. also 50 dgrees would be 12mA.
1500 ma is a amp and a half?
Yes. 1500 mA = 1.5 A
4-20 ma loop testing?
Yes a 4 - 20 ma loop can be tested.
Why is the standard range of ammeter is 4 to 20 ma than 0 to 20 ma?
4-20ma is a standard range used in process controls to indicate measured values. For instance, a pressure instrument may output 4ma to indicate 0 psi, up to 20 ma to indicate 100 psi, or full scale. Or, to control a variable-speed motor drive, 4 ma may mean to stop the motor, and 20 ma to run at full speed. The reason that 4ma is chosen instead of zero is for fail safe operation. A broken wire always results in 0 ma. Suppose our signal right now is 12 ma, and this causes a ventilation fan to run at 50% speed. Suddenly the signal drops to 0 ma. Now, if our range was 0-20 ma, does this change mean stop the fan? Or does it mean the signal wire just broke? There would be no way to tell. With a 4 ma low range, we would know that 0 ma was a broken wire. Then instead of stopping the fan, we could set it to some default speed, or simply continue at the previous speed until the wire was repaired.
Standred voltage used for transmission of 4-20 ma signals?
4ma = 1v rising to 5v @ 20ma
Why is 4 - 20 mA range is used in measuring instruments?
It's a convenient standard for bridge circuits. Also, it allows the instrumentation mechanic to know if a sensor circuit is open, because that channel will read 0ma instead of the lower limit of 4ma.
What is the current in a 100 ohm resistor connected to a 0.40 volt source of potential difference?
V=RI or I = V/R so I = 0.4/100=0.004A or 4mA
Why is 4 mA or 1V is use to represent 0 percent?
In industrial engineering applications, a signal range of 4..20mA is often used to communicate a 0..100% value. The base offset of 4mA allows a distinction between the value zero, and an unavailable value (broken wire, etc). The common 0..10V signal, often supported as an alternative to the superior 4..20mA current signal, does not provide fault detection in this manner. It is possible that applications of voltage based signals exist, where the minimum voltage is 1V. These systems would also provide fault detection in a manner similar to the 4..20mA current signal.
Why 4-20 ma is used in Analog Signals?
Earlier, instead of 4-20 mA, 0-100 mA was used. But the usage of 0-100 mA led to sufficient power dissipation. Hence the upper range was reduced to 20 mA to optimize the power dissipation (this was found by experiments). In this way the upper limit was set. But this 20 mA is limited to cable length of 50 meters. For the lower limit i.e. 4mA . Zero was not used as the lower limit because it give no intimation about actual zero value or zero transmission due to some breaks in the circuitry. Therefore 4mA was set as the lower limit as it is also above the maximum leakage current in electronic circuits. In some transmitters, some times the transmitter shows 2 mA. This is used to indicate that there is some fault in the sensor. Actual zero is indicated by 4 mA. The scale is linear. For example, in a pressure transmitter of range 400bar. 0 bar - 4 mA 100 bar - 8 mA 200 bar - 12 mA 300 bar - 16 mA 400 bar - 20 mA. The reason for not using voltage is that voltage continuously drops over the length of the wire whereas current can be transmitted over a given length without any drop. The main purpose of using electrical quantities is transmission to remote locations.
What devices uses anolog signals?
Generally process control devices use analog signal. Normally in an industrial automation setup, 0-20 mA (mili amp) or 4-20 mA or 0- 10 Volts are used. These signals are used for both providing control output and to provide feed back signal (say to a PLC (programmable logic controller) or DCS) Example for a control out put is a motorized damper operated by 4 - 20 mA signal. PLC provides 4-20 ma signal. Example of a feed back signal is 4 - 20 mA signal from temperature transmitter, measuring a liquid temperature to PLC as input.
What can be used instead of ma-hi ma-hi fish?
shut up your a mama fish
How far is Medford MA from Boston?
The distance from Medford, MA to Boston, MA is 5.9 to 7 miles depending on the route taken. It should take 14 minutes if driven by car or 43 minutes if public transportation is taken.
What are the ratings and certificates for Howard Stern on Demand - 2005 No Signal?
Howard Stern on Demand - 2005 No Signal is rated/received certificates of: USA:TV-MA
What is Armaggedon?
The word Armageddon is taken from the Greek word "Har Ma
Definition of 4-20 mA?
Previously when transmitters were configured for 0-20mA signal it was very difficult to identify an open circuit at 0mA,hence to supersede this defect it was decided to configure the transmitter as 4-20mA signal,so that if there is open signal it can be easily identified.
