What is the current consumption of the eja vortex flowmeter | 24V transmitter

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1. Communication protocol of intelligent pressure transmitter

The reliability and stability of intelligent transmitters are very high, but communication problems are often encountered. Due to the lack of a unified communication protocol standard internationally when smart transmitters were born, the communication protocols used by transmitters produced by various manufacturers are not the same. Typical examples include Honeywells ST3000 using the DE protocol, Fisher Rosements 3051 using the HART protocol, Yokogawas EJA series using the Brain protocol/HART protocol, and a fully digital intelligent transmitter that follows fieldbus communication standards. The main factors affecting the non communication of smart transmitters on site are high-frequency electromagnetic wave interference; Due to the cable being too long, the distributed capacitance of the cable exceeding the network limit, and the low load resistance. The characteristics and potential communication issues associated with each protocol are as follows. 1. HART protocol: HART (Highway Addressable Remote Transformer) is a frequency shift keying (FSK) technology based on the Bell 202 communication standard [2], which achieves digital communication by superimposing frequency signals on a current of 4-20mA. Two different frequencies: 1200 Hz and 2200H, representing "0" and "1", are superimposed in the form of sine waves on a 4-20mA DC signal. Since the average value of these sine waves is zero, no DC component is generated, which will not affect the 4-20mA bending virtual range signal. It achieves true synchronous communication without interrupting the transmission signal. Zhongshan Chemical Co., Ltd. once applied several HART protocol 3051 transmitters

and one vortex flowmeter on site. After being put into operation, they all encountered abnormalities and were withdrawn to the workshop for calibration. The instrument communication and operation were normal. After careful inspection, it was found that a 60 Hz motor and pump were running in the device. To adapt to a 50 Hz power supply, a large number of frequency converters were used, and the carrier frequency of the frequency converters was mostly set to 2000 Hz, which is close to the HART communication frequency and affects the normal operation of the smart transmitter. The problem was solved after adopting the transformation measures of increasing the instrument cable and power cable tray. In addition, using transmitters near smart transmitters and connections can also affect normal communication and operation. The DE protocol represents "1" and "0" based on the amount of pulse current. Digital signals and analog signals are transmitted separately, and when transmitting digital signals, the analog signals must be interrupted. The communication frequency of HART is relatively high (about 1-2 kHz), and the time constant of the network is required to be no more than 0.65 μ s. Therefore, the maximum capacitance of the HART communication device and network limits the maximum distance of communication, which is generally no more than 400m. On the other hand, the communication frequency of the DE protocol is lower, and the maximum time constant of the network is 104 μ s. The allowed cable distributed capacitance is much wider than that of the HART protocol, so there may be a phenomenon where instruments using the DE communication protocol can communicate normally in the same device, but smart transmitters using the HART prot

What is the current consumption of the eja vortex flowmeter | 24V transmitter

1. Communication protocol of intelligent pressure transmitter

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