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
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
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
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
The RK2672AM is a Chinese high voltage test set. This article describes a process for calibration of the device.
This process should not be attempted unless you have the requisite competencies, experience, tools and test equipment. There are dangerous voltages involved, so assess the hazards, plan your work, don’t attempt it if fatigued or alcohol enhanced.
Above is the front panel of the RK2672AM. Continue reading RK2672AM – calibration
The subject vehicle is a Land Rover Defender of mixed heritage. The owner describes the engine coolant temperature (ECT) gauge as useless.
The ECT display system is a dashboard gauge and negative temperature coefficient (NTC) thermistor mounted near the engine thermostat. It measures the engine coolant temperature (hence its name) at the hottest point in the coolant circuit… so it gives the best warning that coolant might be approaching boiling point… and which point cooling capacity catastrophically falls and there is a significant risk of permanent engine damage.
It would seem that Land Rover used many different dashboard gauges, but the underlying electrical characteristics were of just two different types. Likewise there appears to be several different sensors.
The following table of coefficients for four common sensors was derived from published measurements by TSD of a single sensor of each type.
| 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 Diagnosis of engine coolant temperature gauge issue with a certain vehicle
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 10A inline power meter based on an inexpensive module from eBay
Return Loss Bridge – some woolly thinking discussed some online opinions on the practical measurement range of nanoVNA, and underlying reasons… but both were flawed.
Reflection Bridge and Return Loss Bridge are somewhat synonymous, in practice to measure Return Loss one is interested in the magnitude of the response, and to measure the complex reflection coefficient or s11, both magnitude and phase are of interest.
Above is Oristopo’s graph. Continue reading Return Loss Bridge – some woolly thinking – a Simsmith model of a reflection bridge