Home / Guides / Planting, Seeding & Spraying Equipment
Planting, Seeding & Spraying EquipmentSeed Tube Sensors
A seed tube sensor watches seed pass by and reports to a monitor in the cab. It is a helpful set of eyes, but only if the sensors are clean and you know what they actually measure.
Key points
- Seed tube sensors count seed leaving the unit; they do not see seed in the soil.
- Dirt, treatment dust and moisture are the most common causes of false readings.
- Clean sensors with soft tools and keep cables and plugs in good shape.
- Confirm monitor readings by digging a test strip.
What does a seed tube sensor do?
A seed tube sensor sits in or near the seed tube and detects each seed as it falls. It sends a signal to a monitor, which can show seeds per row, skips, multiples or an alarm when a row stops dropping seed. Some systems use the signal to estimate spacing.
It watches seed leave the unit, not seed in the soil. A seed can still bounce, roll or land badly after it passes the sensor, so the reading is a guide to what the meter and tube are doing, not a guarantee of the final stand.
Different systems work differently, and the market changes fast. Read your own manual for what your sensors report.
How do sensors detect seed?
Most sensors use a light beam or similar detection across the tube. When a seed breaks the beam, the sensor counts it. Dust, treatment powder, moisture and scratches on the sensor window can block or scatter the beam and cause false skips or false counts.
Because of that, a monitor that shows a sudden skip on one row may be pointing to a dirty sensor rather than a failed meter. Check before you tear the unit apart.
- Light or beam based detection is common
- Dirt and treatment dust cause false readings
- Moisture and condensation can interfere
- Scratches on the window reduce accuracy
How should you clean seed tube sensors?
Shut down the tractor, lower the planter and remove the key before you reach in. Clean sensor windows with a soft cloth, a soft brush or the method your manual allows. Avoid sharp tools, strong solvents and high-pressure water unless the manufacturer says they are safe.
Seed treatments leave a film that builds up over a day of planting. In dusty conditions, plan to clean every refill or at the intervals the manual suggests.
Check cables and connectors, too. A loose plug causes odd readings that look like a bad sensor.
How do you test a sensor or monitor?
Many monitors have a test mode. Drop a few seeds through the tube by hand or turn the drive wheel with seed in the meter and watch the readout. Compare each row to the others. A row that acts differently from the rest is the one to check first.
Never trust the screen alone. Plant a short test strip, uncover seed in the row and compare what you find to what the monitor reported.
Write down what a normal reading looks like on your planter at your usual speed, so you can spot drift.
What are common sensor problems?
The usual list includes dirty windows, damaged wiring, rodent chewed cables, moisture in connectors, worn seed tubes that change how seed falls, and settings in the monitor that do not match the seed or planter. Dim lighting or a failing power supply can also cause trouble.
Replace damaged parts with ones specified for your planter and monitor. Mixing parts from different systems can cause errors that are hard to trace.
- Dirty or scratched windows
- Chewed or cracked cables
- Moisture in plugs
- Wrong monitor settings
- Worn or damaged seed tubes
How do you read monitor data wisely?
Look for patterns across rows and across the field. One row showing skips for a few feet is different from a row that reads poorly all day. Pay attention to speed, since many planters read best within a certain speed range.
Use monitor data to decide where to dig, not as a replacement for digging. Counts can drift when seed size changes or when a sensor ages, so confirm in the soil from time to time.
If you are shopping for new sensors or a monitor, ask what the system measures, which planters it fits and who supports it locally.
When should you call for help?
If cleaning and cable checks do not solve the problem, ask the dealer service department. Electrical faults on the planter or tractor wiring, communication errors between modules and software updates belong with a qualified technician.
Do not bypass alarms or disable features to keep planting. Fix the cause, since the alarm is telling you something is wrong.
Sources and further reading
- Purdue Extension
- Iowa State University Extension
- American Society of Agricultural and Biological Engineers (ASABE)
- NIST Time and frequency / GPS.gov (GPS info)
Organization homepages are linked so you can search them for current guidance on this topic.