Category Archives: Hydrological Services TB3

Hydrological Services TB3 – Maintenance

This is the tipping rainfall bucket used at most rain gauge sites. Field maintenance is often performed concomitantly with data downloads, so please refer to this when servicing TB3 units.


  1. Loosen three screws at bottom of TB3 and remove circular enclosure
  2. Clean funnel and enclosure using paintbrush and/or damp rag
  3. Turn enclosure over an unscrew syphon
  4. Apply grease to syphon O-ring, if necessary
  5. Remove and clean filter screen
  6. Reassemble filter screen and syphon, hand-tighten back on to enclosure
  7. Remove debris and clean bucket assembly
  8. Verify base is level by utilizing bullseye levels
  9. Reattach enclosure and tighten 3 screws at bottom of TB3

 Annual Maintenance

To decrease the likelihood of lost data, the 3.6V battery in ML1s must be changed each year during annual maintenance runs. Also, rain gages must be calibrated each year.

Dynamic Test

Prior to this dynamic test, disconnect TB3 from the terminal block (preferred) or from the transmitter. After the test is complete, make sure to reattach TB3 and confirm tips via website.

  1. Download data and clear ML1
  2. Place funnel back on top of TB3
  3. Set tripod on top of funnel
  4. Fill calibration cylinder until meniscus forms on top
  5. Screw on 100 mL nozzle taking care not to spill water
  6. Set on tripod, open valve and wait for water to drain out of bottle
  7. Target is 82 tips, but a range of 78-86 (5%) is acceptable
  8. Download data into calibration file and clear ML1 again
  9. If number of tips is out of range, perform static calibration below
Static Calibration
  1. Fill syringe with 10 mL of water
  2. Slowly add water to bucket on one side of TB3
  3. When bucket tips, record volume expelled from syringe
  4. Target is 6.8 mL, but a range of 6.46 – 7.14 mL (5%) is acceptable
  5. Repeat calibration on other side
  6. Use set screws underneath each bucket to increase or decrease the amount of water needed to tip the bucket
  7. Once calibrated, perform dynamic test (above) again