Eaton MTL F809F Plus DTM Operating Instructions

Segment TB: Voltage, Noise, Signal Amplitude, and Number of Devices

Duan TB is the core of on-site troubleshooting. The default low limit for segment voltage is 18V and the high limit is 32V, which should be adjusted according to the actual fieldbus power data sheet. Check the power carrier output, distribution, and wiring for low voltage alarm; High voltage warning for power module and load.

Noise is divided into three levels: low frequency from 25Hz to 3.8kHz, in band from 5kHz to 55kHz, and high frequency from 90kHz to 350kHz. Each level is further divided into average and peak values. The default pre alarm/warning limit for average noise is low-frequency 150/150mV, in band 75/75mV, high-frequency 150/150mV; the default peak value is 65535mV, which is equivalent to disabling to avoid false alarms in the factory state. The typical average noise level on site is below 20mV, with peak values typically below 50 to 60mV. Peaks resembling "spikes" may be caused by lightning strikes, equipment start stop, welding, or temporary short circuits, and short-term disturbances may not necessarily affect the bus; If the average noise continues to rise, it indicates the presence of permanent noise sources such as frequency converters, poor shielding, or parallel AC cables. Therefore, the average noise limit should be stricter than the peak limit.

The troubleshooting sequence for noise alarms is very fixed: check whether the shielding layer of each on-site device is cut short and wrapped properly, and do not have multiple grounding points; Check the shielding connections and grounding inside the on-site junction box, intermediate junction box, and marshalling cabinet; Confirm that the AC power cable is not close to the Fieldbus cable; Confirm terminal fastening; High frequency noise also needs to be checked for welding operations, frequency converter grounding, and nearby high-power radio stations. Attention should also be paid to the grounding of the 5W ERP radio, welding, and frequency converter within a range of 1.5m for in band noise. The short to shield alarm "Short to shield+/- ve" may be caused by the addition of a handheld communicator. If Emerson 475 is used on site, the maximum number of devices should be increased by 1 to avoid false alarms; Otherwise, check for shielding cutting, grounding, floating power supply, and water ingress in cables/junction boxes/equipment.

The default low limit of the device signal amplitude is 150mV, the high limit is 1200mV, the alarm delay is 10mV, and the high limit is at least 20mV higher than the low limit. IEC 61158-2 specifies a range of 750 to 1000mV under testing conditions, but the actual range on site can be from 550 to 1200mV. After debugging, it is recommended to set the low limit of the device to 75% of the current value and the high limit to 125% to make the alarm more realistic while retaining margin. If only one device has a low signal, check the branch cable, branch connector, water inlet, and the device itself; If multiple or all devices are low, check if there are more than two terminals, water ingress, or mainline issues on the segment.

The default low limit for the live list of devices is 0, and the high limit is 32, which is equivalent to no alarm. Connecting a handheld communicator will increase the number of devices. If you do not want to alarm, you can increase the high limit by 1. When DCS itself can detect equipment loss, F809F may repeatedly report a low number of devices, and the default limit value can be retained. The segment retransmission rate is equal to the number of retransmissions divided by the total number of Pass Token requests in LAS, calculated based on the past calendar month; The segment retransmission count can be reset separately, but it will not reset the device retransmission. Resetting the segment count does not affect the retransmission rate, as the retransmission rate is calculated based on the total number of device retransmissions, making it easier to observe newly occurring retransmissions.

The segment diagnosis also provides a "Graph Overview" radar chart, with green areas indicating safe zones and black lines indicating measured values. The black line entering the outer yellow area indicates exceeding the high limit, the outer blue area indicates exceeding the high limit, the inner blue area indicates below the low limit, and the inner yellow area indicates below the low limit. This chart is suitable for quickly determining whether a certain segment is voltage, noise, signal amplitude, or retransmission rate deviation, but it cannot replace checking each parameter item by item.

Device TB: Address LAS、 Signal and retransmission

The device node displays the device address, device tag, signal level, number of retransmissions, and retransmission rate. Addresses 16 to 247 are permanent addresses, 248 to 251 are temporary addresses, and 252 to 255 are used for temporary devices or handheld devices. The devices currently serving as LAS will be labeled with [LAS] after their names, and the backup Link Master cannot be identified solely through bus observation, so the navigation tree will not be marked separately. The typical signal level of the device is between 550 and 1200mV, and retransmission refers to the number of times the device fails to return the Pass Token in a timely manner after LAS sends it and tries again; The retransmission rate is the number of retransmissions divided by the total number of PT requests in LAS.