Logging temperature meter (ltm) is a ESP8266 based temperature measurement and logging device.
Above is the prototype, but for this test a small thin film NTC thermistor was attached to the existing engine coolant temperature (ECT) sensor. Continue reading Logging temperature meter (ltm) v1 – prototype trial run measuring ECT
RF Power Meter 2 is a logging RF power meter based on AD8307 and ESP8266.
The project was used as the basis for a new project, and during that development work some improvements were made and ported back to RFPM2. Continue reading RF Power Meter 2 (RFPM2) – update 04/21
Logging temperature meter (ltm) is a ESP8266 based temperature measurement and logging device.
Snap-On have produced a table of temperature/resistance values for the ECT sensor in the VY 6 cyl Commodore. Continue reading Logging temperature meter (ltm) v1 – prototype VY NTC calibration
N6THN’s novel balun presented measurement of the Insertion VSWR of the subject balun, and N6THN’s novel balun – an explanation gave explanation that included mention of flux leakage as a contributor to the quite high inductance per unit length of the transmission line formed by the two windings.
A correspondent suggested that with a ferrite core, flux leakage is insignificant. This article calculates the coupled coils scenario.
Above is the ‘schematic’ of the balun. Note the entire path from rig to dipole. Continue reading N6THN’s novel balun – flux leakage
This article describes a simple and inexpensive inline power meter for use as a test instrument.
The box cutouts were done on a CNC router, but they could be done with hand tools.
Above, calcs of feeds and speeds for the CNC router. The box is actually ABS, but cutting speed for Polycarbonate is the same.
Above is the tool path for one side of the box. The cutouts suit the 7P-2 strain reliefs. The gcode is generated from a custom Python file using a custom library of common shapes that I use. Continue reading A handy 230VAC 15A inline power meter based on an inexpensive module from eBay
N6THN’s novel balun presented measurement of the Insertion VSWR of the subject balun, this article presents an explanation of why it is so poor.
Above is the ‘schematic’ of the balun. Note the entire path from rig to dipole. Continue reading N6THN’s novel balun – an explanation
One sees lots of articles and videos on how to make a current balun suited to a low VSWR antenna. This one was recommended in an online discussion on QRZ.com. N6THN might not have invented this balun, but he made a video of it.
In this case, it is described in the referenced video as part of a half wave dipole antenna where you might expect the minimum feed point VSWR to be less than 2.
Apologies for the images, some are taken from the video and they are not good… but bear with me.
Above is the ‘schematic’ of the balun.Note the entire path from rig to dipole. Continue reading N6THN’s novel balun
Logging temperature meter (ltm) is a ESP8266 based temperature measurement and logging device.
The project is based on port of an existing ESP8266 Arduino project, and consideration was given to migration to the ESP32 hardware platform, but there are large differences to the WiFi related libraries… so for now, ESP8266 looks ok.
A bigger issue is that the ESP32 ADC is renowned for non-linearity, worse in some modes than others.
One poster offered the following graph of an ESP32 measurement to a discussion.
Some developers have worked on a per device look up table to implement a linearisation scheme. That means each individual device needs to have its input characteristic mapped and then used by the compensation code running on that device. Continue reading Logging temperature meter (ltm) v1 – prototype Vin calibration
Logging temperature meter (ltm) is a ESP8266 based temperature measurement and logging device.
The project is based on port of an existing ESP8266 Arduino project, and consideration was given to migration to the ESP32 hardware platform, but there are large differences to the WiFi related libraries… so for now, ESP8266 looks ok. There remain development options for multi channel logging if needed.
The design criteria are:
The initial algorithm implemented is for a negative temperature coefficient (NTC) thermistor using the single ADC port on the ESP8266. The code uses the Steinhart-Hart model to solve for temperature.
Above is a plot of the Steinhart-Hart model (red) and the so-called B equation (green) for the NTC used in my car. They are quite similar in this case, but the Steinhart-Hart model is more accurate. Continue reading Logging temperature meter (ltm) v1 – a preview
Diagnosis of engine coolant temperature gauge issue with a certain vehicle discussed ECT sensors in a specific context.
The following table of coefficients for four common sensors was derived from published measurements by TSD of a single sensor of each type.
The so-called B equation model is \(T=\frac{1}{\frac1{T_0}+\frac1Bln\frac{R}{R_0}}\).
| Part | R25 | B25/100 |
| AMR3321 | 2246 | 3897 |
| ERR2081 | 2218 | 3879 |
| ETC8946 | 2450 | 3671 |
| AMR1425 | 536 | 4356 |
These are measurements of a single sample, so average values might be a little different. Additionally, the R25 / B25/100 model is only an approximation. Continue reading Engine coolant temperature sensors – a closer look