Technical field

Dial indicators are well known mechanical measuring devices, containing a measuring probe and a display to present position changes of the probe. Said indicators normally have a zeroing function used to set the displayed value to zero at any desired probe position, thereafter displayed values are related to the selected zero position. Performing zeroing requires pressing a button and the force from pressing said button displaces the device and creates an offset in the displayed zero value, this creates a deviation and forces the user to make manual adjustments to achieve an exact zeroed value on the display, This extra operation is undesirable. A purpose with the invention is to facilitate a dial indicator with a zeroing unit that gives a better precision during zeroing compared to dial indicators made according to present technology, and this provided without any separate remote zeroing unit.

This and other purposes are achieved by a dial indicator according to the characterizing parts of the independent claim. Summary

The invention relates to a dial indicator disposed to present measured values for positions of a probe 4 at a display 6. The measured value can be shown in relation to a chosen zero position and the dial indicator is further equipped with a zeroing initiator 3 used to initiate the zeroing of the displayed value for the actual probe position. The dial indicator furthermore includes a zeroing unit that when activated by the zeroing initiator delays the actual zeroing event until the probe is not disturbed from the activation of the zeroing initiator. This improves the zeroing function and enables a more precise zeroing result.

The zeroing unit includes at least a device that receives signals from the probe and admits zeroing event to be possible at earliest when the probe is found to be stable. The zeroing unit may also include one or more of a timer and a three dimensional motion sensor.

Brief description of the figures

Figure 1. Shows a simple type of dial indicator according to present technology.

Figure 2. Shows a more advanced type of dial indicator according to present technology.

Figure 3. Shows a dial indicator according to the invention. Description of embodiments

The invention relates to a dial indicator, thus a device that measure and displays a probes movement from a position. Dial indicators are found in many embodiments, for example analog with a mechanical pointer as well as digital with digit display. Common for these is the possibility of zeroing the displayed value for a selected position of the probe, and the hereafter displayed position values are thereby related to the selected zero position. Performing zeroing requires pressing a button or similar and the force from pressing said button displaces the device and creates an offset in the displayed zero value. This creates a grade of unreliability. Here below are described two different embodiments of dial indicators according to present technology as reference, followed by a description of a dial indicator according to the invention.

Figure 1. Shows a simple type of dial indicator according to present technology, mounted on a magnetic stand 2, with a tuning screw 7. The dial indicator 1, has a digital display 6, that presents a measure value representing the probe position or its position in relation to a selected zero position. In operation, the user chose a desired location for the dial indicator with its probe. Typically thereafter the intention is to obtain measured values form one or more probe positions that represent the divergence from this start position and this is done by pressing the zeroing button 3. The force applied to the button slightly displacing the arms of the magnetic Stand, this displacement is also affecting the dial indicator position away from its intended zero position. The displacement also creates an oscillating movement by the arms of the magnetic stand during the zeroing process. The exact position of the dial indicator at the moment of zeroing is thereby related to some grade of uncertainty and this measurement error is thereafter offsetting all following measures that are based on the zero positon. An alternative solution is to manually tune the displayed value to zero by the tune screw, but this is an undesirable extra and time consuming operation. One other procedure is for the user to note the displayed offset from the zero position and thereafter make corrections to all following measured values in the related measuring series. Also this creates undesirable and extra operation steps.

Figure 2. Shows a more advanced type of dial indicator according to present technology which, in contrast to the earlier mentioned type has a switch connectable by a cable 5, this enables the user to initiate zeroing without touching the dial indicator. There are also versions of these advanced dial indicators that use radio or infrared signals to initiate zeroing from a remote control device. These solutions apparently eliminate the need to bring force to the actual dial indicator to initiate zeroing, but these types of dial indicators are usually high end products and are more costly devices.

Furthermore do these solutions contain extra remote devices that are connected by cable or cordless signals, this becomes more complicated for the user. Figure 3. Shows a dial indicator according to the invention, just like the simpler type of dial indicator of present technology it contains a zeroing button 3, placed directly on the dial indicator. To avoid a risk of introducing measuring errors this dial indicator has added functionality to ensure the zeroing event not to occur simultaneously to the moment of pressing the zeroing button, but instead to have the zeroing event to happen when the measuring arrangement has stopped oscillating at some time after activating the zeroing button.

This can be achieved in a number of methods and the simplest way is that the dial indicator comprises a timer functionality that delays the zeroing event to happen a preset time after activating the zeroing button. Apparently this timer can in one embodiment be adjustable for the user to select how long the delay shall be until the zeroing event shall happen. This is of significance as the arrangement with the dial indicator and its suspension in different situations can be oscillating different length of time.

Another way is to have a function where the signal from the probe in the dial indicator is evaluated and thereby get information about if the measurement arrangement movements have ended, but if the dial indicator is stable but displaced from its intended zeroing position is not possible to evaluate with this method. Thereby it may be of interest to combine these two above mentioned methods to get a safer way of evaluating if the dial indicator really is stable and in the intended position. This can be done by evaluating the signal from the probe in the dial indicator and when the signal indicates that the probe is stable the timer is started and delays the zeroing initiation, until a set time has passed.

The signal from the probe of the dial indicator can only give information about movements in the same direction as the probe travels, In other words along one axis. To further ensure that the dial indicator has its intended position during the zeroing event, the dial indicator can be equipped with an accelerometer or any other type of motion sensor that measures motions in 3 directions.

Information from the accelerometer is then used in the same manner as described for the signal from the dial indicator probe to evaluate that the dial indicator has reached a stable position.

Regardless of what sources of data the dial indicator use or how these are used, are these all here designated as zeroing unit. The zeroing unit is thus a unit that evaluates whether the dial indicator, after that zeroing is initiated, no longer is disturbed by direct influence from the users finger and nor is in motion by oscillations. The zeroing unit can in other words be as simple as a timer that delays the zeroing a fixed time from the occasion when it is initiated by pressing the button, yet it can also be a lot more advanced and utilize data from the dial indicator measuring probe, from

accelerometers, from presence sensors or other types of sensors and combine data from all these in various ways. Obviously the zeroing unit can practically be a part of a software in an already existing processor used in a dial indicator and can in this case not be physically separated from the rest of the dial indicator, but what is meant obviously is the referred function in that software, even if it runs in the same processor as the rest of the dial indicators functions.

The presented embodiments include a digital display included in the actual dial indicator, but obviously there is no need for the display to be digital, and may in some cases not even be direct integrated into the dial indicator. In some versions of the invention there may be a total absence of own display, where the measure data are presented on a computer or similar and in such case the computer monitor is the display referred. Obviously there may be similar variants of the invention where the dial indicator does not consist of a coherent physical unit but rather is divided with the functions located in physically separated parts that interact in precisely the manner presented. The object that here is denoted as probe obviously includes all variants of objects with the corresponding function, such as for example a lever arm or such.