Emerson 250, 350 operation manual Power Supply Troubleshooting, General Troubleshooting

Models: 350 250

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2.Water damage to the electronics module or sensor probe. This is potentially the most severe case the symptoms are unpredictable. If there is any suspicion that the transmitter may have incurred water damage please contact the factory to make arrangements to have the unit sent back for factory inspection.

Physical and water damage are not covered under warranty.

3.Magnetic Indentation. It is possible for any magnetostrictive instrument to have residual magnetic energy stored along the length of the waveguide. These magnetic anomalies can interfere with the output response signal. If this appears to be the case a level gage float (or a bar magnet preferably) may be run along the length of the sensor tube, past the head of the transmitter, in an even motion without stopping. This will usually clear all such magnetic anomalies.

Never move a magnet in perpendicular motion away from the sensor tube. This will always leave a residual magnetic field in the waveguide which causes the transmitter output to be erroneous or unstable.

The LTM-350 is HART compatible, however HART communication will not work if the unit is not powering up.

8.2 Power Supply Troubleshooting

The LTM-250/350 is designed to operate with a supply voltage of 13 – 36 Vdc (minimum 13V @ 20mA) across its terminal without affecting the analog current output. The most common supply voltage used is 24Vdc.

At times additional resistance in the loop is necessary, either in the form of a second load resistor or higher resistance safety barrier. This will appear to limit the maximum output of the transmitter to below 20mA. The transmitter will perform correctly up to a certain point. To resolve this problem, the voltage of the loop supply must be increased. Even a slight adjustment of 1Vdc may be sufficient.

All connections must be checked for improper wiring or polarity before power is applied. LTM- Series transmitters are polarity protected.

8.3 General Troubleshooting

Below are some troubleshooting procedures for the LTM transmitters that have been established overtime.

Symptom: Transmitter is not powering up. The LCD is not turning on.

Resolutions:

1.Make sure power is applied correctly (meaning plus and minus are not reversed). The transmitter is polarity protected.

2.Make sure the electronics module is seated properly. Open the front cover (where the LCD is) and firmly push on the “Magtech” text. A good way to tell if the electronics are not seated properly is by making sure the protection screws are not physically higher than the outside of the housing. Sometimes pulling the electronics module out and putting it back in can reseat the electronics correctly. Use cutters or needle nose pliers to grip the protection screw and lightly pull on each screw (alternate).

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Emerson 250, 350 operation manual Power Supply Troubleshooting, General Troubleshooting