# Benchmarking 1930s Calipers

So recently I got this set of 1930s calipers: So now the question is: How accurate are they? Let’s find out! I’m using a 25mm micrometer calibration piece, but before we can use it, let’s assess what different instruments say about this piece to get a tolerance range. Note that none of those are professionally calibrated, I’m just doing ballpark measurements. The Micron Metrology micrometer I’m calibrating with this calibration piece says it’s lightly below 25mm, both the instrument and the piece is quite cold however, as I had them in an unheated room and it’s winter.

# Electrical Distribution Panel for my Workshop

So far my Workshop was connected to a 25A (“L” class) circuit breaker back from the 70s or so and also no FI (RCD). Which isn’t really that safe, especially not in my workshop. Since getting the electrical distribution panel for the house up to standard is currently out of the question, I decided to build myself a sub distribution panel, to at least have a somewhat safe workshop environment.

# Fixing a Microscopy XY Stage (Objektführer)

On various platforms you can get cheap XY stages (Objektführer) of various designs, because quite often it is hard to get the ones specific to your microscope. I originally got the one on the right for one of my upright microscopes but then noticed it also fits onto my MBS-10 stereomicroscope. However it has the knobs to the side which doesn’t work with the base of the MBS-10. So fair enough I ordered one with knobs on the top (the left one).

# Readout Electronics: High Voltage -1.25kV PMT Bias Supply

This is part of my readout electronics system. This is an adjustable high voltage power supply I built for biasing the dynodes of photomultiplier tubes (PMTs). It uses a Hamamatsu C4900 high voltage DC-DC converter. Control can either be local (potentiometer on the front panel) or remote (external 5V DAC). The orange LED on the front panel indicates that remote control is active. Whether the unit is in local or remote control is controlled from a microcontroller on an external board.

# Readout Electronics: Wideband Pulse Amplifier

This is part of my readout electronics system. A high speed amplifier unit I developed a while back, mainly to amplify fast PMT pulses. It uses two uA733 pulse amplifiers with a gain of 20dB, at around 200Mhz with a rise time of 2.5ns. The output of the first one can be inverted with the switch on the front of the unit, which then switches a soviet reed relay (РЗС55А 1101) to select the output.

# Readout Electronics: TTL/CMOS Dual Divide-by-10 Scalar

This is part of my readout electronics system. It uses two CMOS 4017 decade counters. The resistors are for current limiting and there are input protection diodes. The reset for both ICs can be triggerd by the small micro button. Speed is fairly moderate, around 5Mhz with required pulse widths of 60ns.

This is part of my readout electronics system. This is a fairly simple ±5V 500mA preamplifier power supply I designed originally with Hamamatsu PMT preamplifiers in mind, but I ended up not getting one of those. So now I’m using it for my own preamplifier modules. The circuit is a fairly standard LM317 and LM337 one with stability improvements by adding a capacitor (and associated diode) to the programming pin. See the data sheets for any LM317 or LM337 for the circuit.

# Stabilized Linear 2,5A 12V Power Supply

The other day I built this power supply out of components I had lying around. In particular I had this enclosure sitting on the shelf for years now and wanted to finally put it to use and also a toroidal transformer I also had sitting in the shelf. Unfortunately I didn’t take any pictures while building it only after the fact. Here is the schematic, fairly standard and self-explanatory, it uses a 2N3055 transistor and a Zener diode.

The following is from my notes I did a while back, whilst evaluating different numerical quadrature methods. Quite a lot of numerical quadrature in software used seems to be Gauss-Kronrod, in particular derived from QUADPACK. Any thoughts or corrections? Drop me a mail. Gaussian Quadrature Gaussian quadrature approximates integrals in the form of: $$\int^{b}_{a}f(x)\ dx$$ For some range $$a$$ to $$b$$ inclusive or exclusive depending upon the type. With a sum in the form of: $$\int^b_af(x)\ dx\approx\sum_{i=1}^nw_if(x_i)$$ Where $$w_i$$ is some weight and the node $$x_i$$ being the root of an orthogonal polynomial.