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I had a plastic ruler at one time in my life and it looked something like Figure 1. Figure 1. Overview. Figure 2. Close up of precision grid. Figure 3. In-use. How to use: Align the right edge to the nearest whole cm less than the width of the item to be measured. In the precision section, find the closest intersection between a sloping line and a ...


4

Metric bolts use thread pitch in millimeters. Your M3 screw likely uses the standard pitch of 0.5 millimeters. One complete rotation of the screw will advance the screw into the work piece by that amount. According to the Bolt Depot chart, there is only one standard pitch for M3 screws, although other sizes will have standard, fine, super fine pitches ...


3

A metric thread table is what you want. Table 1. Source: Anzor. So is there a standard rule of thumb, or equation about the distance the end of a screw will travel per rotation? It's not a rule of thumb - it's defined by the pitch. Conversely, how many turns it will take to travel a specific distance? Turns required = distance / pitch. Say I have ...


3

Hair is mostly transparent to ultrasonic, so this is still the reliable&convenient approach - any EM spectrum readouts (3D, video, laser) will be completely falsified by hair. You just need a narrow cone ultrasonic sensor - one with readout area restricted to top of the head. It's not something to be found in robotics/industrial equipment supplies, but ...


2

I do not believe this will be an effective scheme. The $Q$ of a resonator, a number which describes the strength of the resonant peak, is given by $$ Q=\frac{f_0}{\delta f}\approx f_0\frac{2\pi\ t_{RT}}{\ell}, $$ where $f_0$ is the resonant frequency, $\delta f$ is the FWHM of the resonance, $t_{RT}$ is the round-trip time, and $\ell$ is the round-trip ...


2

I'd put this in the not possible/very difficult category. Simply because if you are dealing with RF your wavelength is going to be on the order of 10cm - 1m+ which is going to place a limit on the accuracy you can achieve with any simple method. I'd be interest if thinks it can be done and how. For other methods I think stereo vision or structured ...


2

How about using a Capacitive Fluid Level Sensor from Molex. The sensing element can be affixed outside of the tank. Here is an image of the sensing element affixed outside of the a container. . Below is an expert from the product website. Capacitive Fluid Level Sensors easily mount to the outside of a container and measure through almost any non-...


2

I would give a shot at image processing, if there is a good contrast between the surface you want to measure and the background. To do so you need to take a picture of the surface that includes an object of known size for calibration. Then, open source software like "imageJ" are able to perform the measurement. The accuracy of this method strongly depend on ...


2

50μm → 0.002" or 2 thou or 2 mils? I've seen both 0.002" and 2 mils. On a drawing it would always be 0.002". In a specification document it could be either. I've never seen 2 thou written in a formal specification (but I have heard people say it in the shop). But that might just be my experience. There could be variation from industry to industry. Is ...


2

I've had the possibility to test several different diagnostic ultrasound devices in a big bucket of water with gravel at the bottom! The result is interesting: At first, for all devices you have to use a "curved sound head", the linear one doesn't work at distances further than a few centimeters. With cheap devices I could hardly see the bottom or the gravel....


1

Forget PID at first. If we assume PID, we're skipping steps. Write down what we know. From your description: process variable : position input : (other robot's position - following distance) loop output : this robot's position plant input : velocity plant output : this robot's position plant dynamics : simple integrator Now we can draw a system diagram: ...


1

I do work for a company that makes sensors that might be applicable. These sensors are used, among other places, to measure levels in ballast tanks of ocean-going ships. The possible gotcha for your case is the size of the tank. These sensors are meant for tanks depths of a few meters at least, up to 30 meters or so. When the tank is too small, the ...


1

Typical distance sensors depend on time-of-flight. If you're trying to hack the distance from return power level, you will not be happy (to put it mildly). It's next to impossible to calibrate any system that way. As to direction, it should be obvious that you cannot possibly do so with a single receiver. As a minimum you'd need two sensors aka two ...


1

Yup, You could use something as simple as a bar clamp. Most hardware stores will carry some version. The type you'd need is the type that can be reversed to a spreader (95% of them can do this just double check). With one of these you'd need something to connect your cord to it. But still fairly straight forward (more clamps for example. This wont be ...


1

If you are at a university, you can consider using a universal tensile testing machine to stretch the rubber cord at specific stretch rates. Otherwise, you may develop a simple setup using stepper motor to also stretch it at fixed stretch rates.


1

Maybe you could use one of the following: level glass allows you to read the height of the liquid outside the tank. The width of the tube would have to be large enough for capillary action to be neglectable If there is a lot of movement inside the tank the water level in the tube might oscillate as well. Electronic hydrostatic manometer ...


1

I think you have approached your problem from the wrong direction. There are currently no sensors that measure distance between each other regardless of material in the path. It would be possible to make a device with optical or ultrasonic time of flight technology, but that would be a project all by itself. These sensors are very expensive and need ...


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