Measuring torque and speed at the tractor power take-off during field work
In brief
A PTO transducer is splined between the tractor and the implement: its female spline mates with the PTO shaft, its male spline with the implement, and both ends lock. It measures the torque, up to ± 2 500 or ± 5 000 N·m, and the speed from a 60 pulse per revolution encoder, and their product is the mechanical power delivered at the take-off. The PTO sends its signal by induction-powered telemetry; the PTO2 reads its bridge through an integrated slip ring.
- ± 2 500 or ± 5 000 N·m
- full-scale torque, by spline size
- 60 ppr
- Hall effect speed encoder
- 3 kHz · 1 kHz
- sampling and bandwidth of the PTO telemetry
Mounting
The torque in the power take-off shaft is an input to the development of the tractor transmission; with the shaft speed measured at the same point, it gives the power delivered to the implement. The shaft links two machines that stay as they are, and its splines differ: type 1 is 1 3/8 in (35 mm) with 6 teeth, type 2 is 1 3/8 in with 21 teeth, type 3 is 1 3/4 in (45 mm) with 20 teeth.
The transducer goes on the PTO shaft and the implement on the transducer. On the PTO, an anti-rotation eye-hook keeps the stator from turning. On the PTO2, two spline locking blocks held by eight M4 screws lock the female spline onto the groove of the tractor shaft, and two spring-loaded restraint cables, routed in opposite directions to fixed parts of the tractor, hold the slip ring stator.
Transducer
| Full-scale torque | ± 2 500 or ± 5 000 N·m · on the PTO2, 2 500 N·m with 1 3/8 in splines, 5 000 N·m with 1 3/4 in |
|---|---|
| Non-linearity, hysteresis | ≤ 0.5 % FS |
| Speed | 60-tooth tone wheel and Hall effect sensor, 60 ppr |
| PTO | integrated telemetry, induction-powered stator on a sealed bearing · 3 kHz sampling, 1 kHz bandwidth · removable splined ends for types 1, 2 and 3 · 5.8 kg with a 1 3/8 in spline · −40 to 105 °C |
| PTO2 | 350 Ω full bridge read across an integrated B4-2W/E60 slip ring · one spline size per transducer, 1 3/8 in-6, 1 3/8 in-21, 1 3/4 in-6 or 1 3/4 in-20 · 3.7 kg with a 1 3/8 in spline · slip ring also non-weatherproof, with or without encoder |
| Supply, PTO | 11 to 15 V DC, 3.0 A max for induction power and receiver |
| Delivery | pre-calibrated, with its calibration certificate |
Signal path
On the PTO, the telemetry transmitter excites the strain gages, amplifies and digitizes the torque signal and transmits it by radio to the receiver; the non-rotating stator carries the primary induction coil, the receiving antenna and the Hall effect sensor. On the PTO2, the torque signal leaves through the connector on the slip ring stator and the speed signal through the connector of the Hall effect sensor; the Transducer Display Module adds signal conditioning, an analog output and a display.
Procedure
- 01
Match the spline
Check the spline of the tractor and of the implement. The PTO changes its splined ends for types 1, 2 and 3; the PTO2 is made in one spline size.
PTO torque transducers - 02
Fit and lock both ends
Transducer on the PTO shaft, implement on the transducer, both ends locked; eye-hook on the PTO, two spring-loaded cables on the PTO2.
- 03
Connect the receiver
Induction power and receiver on 11 to 15 V DC for the PTO; slip ring and encoder connectors for the PTO2.
PTO2 with slip ring and encoder - 04
Record torque and speed
Both channels during implement work; torque times speed gives the power delivered.
Result
The torque and the speed at the power take-off, and so the power delivered to the implement, with the machine and the implement unchanged.
Frequent questions
How is the power at a tractor PTO measured?
Torque and shaft speed are measured at the same place, and their product is the mechanical power delivered at the take-off. A PTO transducer measures both, with a 60 pulse per revolution encoder.
Does the tractor or the implement have to be modified?
No. The female spline of the transducer mates with the PTO shaft of the tractor and the male spline with the implement. An eye-hook on the PTO, or two spring-loaded cables on the PTO2, keep the stator from rotating.
Which PTO spline types can be measured?
The PTO has removable splined ends for the agricultural standard types 1, 2 and 3. The PTO2 is made in one size: 1 3/8 in with 6 or 21 teeth, or 1 3/4 in with 6 or 20 teeth.
What torque range do PTO torque transducers cover?
± 2 500 or ± 5 000 N·m full scale, with non-linearity and hysteresis at or under 0.5 % of full scale.
Similar applications
All applications-
Agriculture Agricultural machinery Wheel loads, wheel torque, PTO power and forces on working parts, measured on the machine at work. -
Agriculture Combine harvester gearbox Torque, speed and temperature on the pulleys, gears and gearboxes of a combine, to find power losses. -
Powertrain Axle and half-shaft torque Drive torque measured on the production shaft, with a slip ring or telemetry to bring the signal out.