Understanding valve offsets and gains

Incorrect valve offsets or gains can cause performance issues, and it is important to ensure that they are set correctly.

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Understanding valve offsets and gains

Hydraulic calibration

The Topcon system has two hydraulic adjustments:

  • Valve offsets: Set the minimum signal to open the valve.
  • Valve gains: Adjust the speed of the cylinders, which is related to grade error (how far from grade).

Valve offsets can be accessed by going to Control > Control Settings > Valve offsets…

Depending on your version of 3D-MC software, your screen may look slightly different. However, the procedure is the same.

Valve offsets

There are four valve offset calibrations for the four movements the system will control.

The valve offsets should be set with the machine running at high RPM.

Click the Set button next to the respective offset to begin.

Once the Set button is enabled, a set of up and down arrows will allow the operator to adjust the value one digit at a time.  

Proportional output

The output "flow" is proportional to the electronic input command. The valve offsets set the minimum input command to begin the output flow. From there, the gains will increase the input command to provide proportional flow.

Valve offsets

Setting the valve offsets is a process of increasing the valve offset value, which in turn increases the input signal to the valve.

When the valve receives enough input, the hydraulic flow will begin.

We are looking for the minimum offset value that is indicated by hydraulic flow, which can be seen when the corresponding cylinder begins moving.

Valve offsets hysteresis

Hysteresis causes imperfect offset adjustments. From the graph, you can see that input voltage or current is higher to get the flow started and may be lower to stop the flow. The difference between an offset value to open the valve and close the valve is the valve's hysteresis.

Ideally, you would like a small hysteresis for the best performance. Typical hysteresis can be about 10 points.  So if a value of 200 starts the hydraulic flow (cylinder movement), typically a value of 190 would stop the hydraulic flow.


Valve gains

Think of the gains as a valve offset multiplier:

  • The higher the gain, the higher the valve output as the grade error increases.

With the offsets set, the gains can be adjusted.

With a gain of 1, you will only get the offset value regardless of the grade error.

With a gain of 50, as the grade error increases, the valve output increases.


There are gains for elevation and gains for slope.

Elevation gains are accessed through the Elevation tab.

Slope gains are accessed through the Slope tab.

Elevation gains

Gains are best set when operating the machine in the field. However, setting them when the machine is static can be achieved.

With an active surface, raise the blade approximately 300 mm (1’) in the air, and match that elevation.

Lower the blade until the display indicates that the blade is below the grade by about 100 mm (0.32’).

  • The standard working window is 120 mm (0.40’).

If you switch the blade into auto, the blade will raise to grade and should stop on grade.

Perform the same for the lower correction, and slowly increase the gains so the blade moves as fast as possible with the least amount of overshooting.

Typically, you will find that when properly set, the raised gain will be higher than the lower gain by a ratio of 2:1 for dozers. Graders may not have the same ratio.

Slope gains

Gains are best set when operating the machine in the field. However, setting them when the machine is static can be achieved.

With an active surface, begin by tilting the blade CW or CCW, and turn the system into auto. Evaluate the slope reaction speed.

Increase the CW and CCW gains until you can get the fastest corrections with the least amount of overshooting. Adjusting the slope gains statically can be more sensitive than setting the elevation gains.