The short answer
How to Configure a Radar Level Transmitter
To configure a radar level transmitter, mount it with a clear view of the surface away from walls, inflows, and obstructions, enter the distance from its reference point to the vessel bottom and the span you want as 4 to 20 mA, run a false echo mapping with the level as low as possible so the transmitter ignores fixed reflections, set damping for the application, confirm the output direction, and verify the reading against a tape measure at two levels. Record every setting and the elevations they were derived from.
Key points
- The reference point is on the transmitter, and every distance is measured from it. Find it in the manual first.
- Range settings come from a tape measure, not from the drawing.
- Map false echoes with the well as empty as it will get. A map made at high level hides the obstructions below.
- Damping smooths the reading and delays it. A few seconds on a wet well; less on a fast process.
- Verify at two levels. A one-point check cannot find a span error.
What you need
- The transmitter manual, with the reference point drawing and the menu structure
- A HART communicator, the manufacturer software, or the local display
- A tape measure long enough to reach the bottom, with a weight
- A loop calibrator or milliammeter for the output check
- The instrument list with the intended range and the controller scaling
- The mounting hardware: a flange or bracket that places the antenna where it needs to be
Procedure
- 1
Find the reference point
The manual shows where on the transmitter the measured distance starts: the flange face, the antenna tip, or a mark on the housing. Every range setting is a distance from that point. Getting this wrong offsets every reading by the difference.
- 2
Check the mounting
The antenna perpendicular to the surface, with a clear cone of view to the lowest level. Away from the wall by the distance the manual gives, away from the inflow stream and the pump discharge turbulence, and not above a ladder, a pump cable, a guide rail, or a float that swings through the beam. A nozzle or standpipe must be the size and length the manual allows, or the echo comes from the nozzle.
- 3
Measure the distances
With the tape, from the reference point to the vessel bottom or to the lowest point you want to measure. Note the elevation of the reference point against a site datum if elevations are used. Measure the current level at the same time, from the reference point to the surface.
- 4
Enter the empty and full distances
Empty distance, the distance from the reference point to the 4 mA point, usually the bottom or the low-level cutoff. Full distance, or span, the distance from the reference point to the 20 mA point, usually near the top of the range with margin below the antenna dead band. These two settings define the output. Copy them from the tape, and copy the resulting range to the instrument list and the controller scaling.
- 5
Set the application parameters
Medium type, liquid; vessel type, open or closed; surface condition, calm or turbulent; and for wastewater, the fast-changing or agitated surface option if offered. These tune the echo processing.
- 6
Run the false echo mapping
With the level as low as it can safely go, so that as much of the well as possible is in view, run the mapping function. The transmitter records the fixed echoes from the walls, the pumps, the rails, and the inflow pipe and ignores them thereafter. Mapping with the well full records nothing useful and leaves the obstructions below the surface unmapped.
- 7
Set damping
The time constant applied to the reading. Two to five seconds on a wet well smooths turbulence without hiding a real change. Less on a tank with fast fill and draw; more on a very turbulent surface. Damping delays every change by about its value, so keep it short enough for the control.
- 8
Set the output and failure behavior
Direction, 4 mA at empty and 20 mA at full unless the loop is designed otherwise. Failure current on lost echo, high or low per the site standard, so the controller can detect it. Echo-lost timeout, the seconds the transmitter holds the last value before declaring a fault.
- 9
Verify at two levels
At the current level, compare the transmitter reading with the tape. Then at a second level, after the pumps have moved the well or by pumping down deliberately, compare again. Both should agree within an inch or two. A consistent offset at both is the reference point; a difference that grows with level is the span or the empty distance.
- 10
Check the loop and the controller
Read the output current with the calibrator at the panel and confirm the controller shows the tape reading in engineering units. Confirm the low-level cutoff and the pump setpoints in the controller correspond to the elevations intended.
- 11
Record
Reference point location, empty and full distances, mapping level, damping, failure current, the two verification readings, and the date, on the loop sheet and the instrument list.
Settings that cause trouble
| Setting | Symptom when wrong | Fix |
|---|---|---|
| Empty distance from the drawing, not the tape | Constant offset at all levels | Measure and re-enter |
| Mapping done at high level | Reading jumps to a fixed value as the well pumps down past an obstruction | Re-map at the lowest level |
| Dead band ignored | Reading stuck at full when the surface rises near the antenna | Lower the 20 mA point below the dead band, or raise the transmitter |
| Damping too long | Level lags; pumps overshoot the stop setpoint | Shorten damping; check the controller filter too |
| Failure current same as a valid reading | Lost echo looks like a real level | Set failure current outside 4 to 20 mA and validate in the controller |
| Nozzle too long or too narrow | Reading fixed at the nozzle end | Shorten the nozzle, use the correct antenna, or map it if the manual allows |
Verification
- Transmitter reading agrees with the tape at two levels at least a foot apart.
- The controller displays the tape reading in engineering units.
- The reading follows a pump-down smoothly through the full range without jumps at obstructions.
- A blocked or lost echo produces the configured failure current and the controller alarms it.
- All settings and the measured distances are recorded on the loop sheet.
Frequently asked questions
- Why does the level jump to a fixed value part way through a pump-down?
- An unmapped fixed echo, usually a pump, a rail, or the inflow pipe, that the transmitter starts tracking as the surface passes it. Re-run the false echo map with the level below the obstruction.
- Can I configure the transmitter with the well full?
- You can enter the distances and set the output, but you cannot map the false echoes usefully, and the two-point verification needs a second level. Enter the settings, then finish the mapping and the verification at low level, even if that means a return visit.
- What about foam and grease on the wet well surface?
- Radar reads the top of foam poorly and a grease mat inconsistently. Higher frequency radars with narrow beams do better; the application settings help; and where the surface is regularly covered, a submersible pressure transmitter as the second measurement with cross-checking in the controller is the practical answer.
- Should the empty distance be the bottom of the well?
- It should be the point you want to read as 4 mA, which is usually the bottom or a little above it, below the low-level cutoff. Setting it at the cutoff loses the ability to see the well below that level, which is useful for a dry-run diagnosis. Setting it far below the bottom wastes range.
Related topics
- Radar Level MeasurementNon-contact and guided wave radar, why it handles a wet well better than most alternatives, and the installation details that decide whether it works.
- Wet Well Level MeasurementHow lift station wet well level is measured, which technology suits which well, the failure modes that flood a station, and why the high level float must stay hardwired.
- How to Scale a 4-20 mA Input in a PLCTurn raw analog counts into engineering units, verify at three points, and add the validity checks that stop a failed transmitter from producing a believable number.
- Signal ValidationCatching a failed analog input in logic before it runs a pump on a dead transmitter: range checks, module status bits, frozen-value detection, rate checks, and what the program does with a bad value.
- Wet Well Level ControlThe measurement that runs a lift station: choosing setpoints, protecting the pumps, validating the signal, and the failures that flood a station.
- How to Calibrate a Pressure TransmitterA five-point calibration with a pressure source and a reference: isolate and vent, record as-found, decide whether to adjust, trim the sensor and the output separately, verify as-left, and record it so the next calibration means something.
Direct contact
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