Transmitter calibration
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I currently have several transmitters installed: EJA110A, EJA430E, EJA118E, and EJA530E. All of them are HART type and need to be calibrated. Can I use a 375 device for this? Can I simply connect the meter to the two terminals of the transmitter? The diagrams online all suggest using a 250-ohm resistor – is that necessary? It would be great if there could be an image; thank you to all fellow sailors for your help in providing answers!
As long as it is a Hart protocol, two-wire systems can be directly connected to the two-wire terminals. If communication fails, a resistor of around 250 ohms should be inserted in the mA circuit, and then the system can be connected across both ends of that resistor
If the transmitter is already connected to a safety barrier, it can be directly connected to the handheld controller; if it is connected to a switching power supply, then a resistor needs to be connected in series. It is recommended to use a safety barrier that already comes with a resistor
Just connect it directly to the terminal; if there is no communication, then connect a resistor in series
The EJA is from Yokogawa, and generally speaking, Yokogawa’s Hart devices are not very good. If it’s already installed on site, it can be connected directly to 375. Give it a try first
Some time ago, I’m not sure if I got a fake EJA unit – the differential pressure and level readings kept fluctuating randomly... I took it back and adjusted it twice before it started working more properly
If it has already been installed on site and connected to the indoor instruments, then there is no need to connect a 250-ohm resistor in series. If the transmitter is to be calibrated directly indoors, a series resistor is required for calibration and setting.
Hang it directly on site; if that doesn’t work, try connecting a resistor
The Yokogawa transmitters with Hart communication really make one cry – in the scorching heat, it’s impossible to operate them outside; then one has to search everywhere for resistors, which is utterly frustrating. If you need to decide on a brand to purchase, I would recommend Rosemount; it’s not out of favoring foreign brands – it’s simply very reliable
When a resistor is used for indoor calibration and none is used for outdoor calibration, how can it be determined whether it is indoor calibration or outdoor calibration?