I’ve been playing with some very cheap, but quite good power meters made by Eastron for a few years now, in particular their compact (single-DIN) single phase Modbus meters. They are great for cheap (non-commercial) energy monitoring applications. The SDM120M variant has Modbus over RS-485 support for convenient data acquisition and integration. These aren’t the […]
Note: This post is currently just some loose notes during my R&D, and is a continuation of the Extech CO250 project. See my Extech CO250 review here. I have RS-232 details and teardown here. Open-source Java library I have a working Java library that reads all values over serial and provides statistics (minimum, maximum, average, […]
The Extech CO250 (AKA Senseair pSENSE RH) is a relatively cheap handheld air quality measurement device with decent features. It measures carbon dioxide (CO2), dry-bulb temperature, and relative humidity, and also provides calculated dew-point and wet-bulb temperatures. One interesting feature, and the subject of this post, is it’s serial communications port. It comes with a […]
The Extech CO250 is a relatively cheap handheld air quality measurement device with decent features. It measures carbon dioxide (CO2), dry-bulb temperature, and relative humidity, and also provides calculated dew-point and wet bulb temperatures. After some searching I found what seems to be the OEM device which Extech rebadges. The original device seems to be […]
In this video we take another look at the RS-232 plug-in module for the Sanden PET-07 CC/CV power supply. In particular, we see how the voltage output can be controlled and how this clears up some ambiguity with the circuit design. In part three, we will *finally* attempt to communicate using RS-232 to monitor and […]
In this video we take a look at the Sanden PET-07 CC/CV power supply. In particular we look at the RS-232 plug-in module and attempt to make sense of the signals between the main board and plug-in board. In part two, we’ll apply this knowledge to attempt to receive RS-232 data from the power supply. […]
Here’s some photos of the Protek 608 RS-232 cable teardown: Bill of materials You know a teardown is serious when a BOM is produced! 😛 This may be overkill, but I have plans in future to develop my own transceiver hardware that instead of using RS-232 to connect to a PC, it will use a […]
As detailed in a previous post, the physical communications layer is RS-232 – 9600 baud, 7, N, 1. So we know how to correctly connect the the multimeter and handle the data transfer, but how is the data interpreted? What’s the language or meaning? In this post I detail all of this, starting with the […]
This is following on from my previous post introducing the Protek 608 multimeter and my software project. In this post I detail the communications hardware, an important consideration for future development. The Protek 608 uses an RS-232 connection to allow for interfacing with a PC. This is a very common connection that most DMMs used. […]
The Protek 608 is a 5000 count digital multimeter made by Hung Chang, who have since changed their name to GS Instruments. I’ve owned one of these since about 2009. This multimeter is now discontinued and no longer available new, although they occasionally show up on the second-hand market from forums and eBay. This DMM […]