UNIVERSAL BUFFERS / ISOLATORS EXPAND THE APPLICATION RANGE OF PICOLOG DATA LOGGERS
The buffers/isolators to be presented in this series provide additional features to the above mentioned data loggers, as follows.
1. Each buffer provides 6 isolated input channels to the DA Logger. Adding this device to the DA separates the DA ground terminals from the sensors' grounds, which will become completely independent, with a ground to ground isolation exceeding 1 kV.
2. In the last two years there has been a remarkable migration from sensors having an analogue output, to sensors having digital output. In general the digital output sensors afford a higher level of precision and stability. Furthermore, with the loss of two inputs, the buffer makes available a standard I2C input which can read one or more digital output sensors. The buffer then converts the I2C input into a 0 - 2.5 V analogue output that serves the analogue input of the Picolg DA. With this facility the DA will afford four isolated channels and one to several digital input channels, depending on whether or not I2C multiplexers are used.
3. Initially an 8 Bit buffer will be presented and illustrated, based on the Arduino 1 Micro. This buffer / isolator works with very simple software and employs a minimal number of external components. With a few modifications it will also work as buffer for the DrDAQ Ext. Channels. Standard or clone micros can be used. A Clone micro can be purchased today for less than £ 5.
4. Later on a 10 to 12 Bit buffer, affording no compromise on resolution, will be presented and illustrated, based on the Arduino Zero Micro. The writer's work on this recently introduced device, for which very little technical information is presently available, has progressed very well. The new software developed obtains greater resolution as a trade-off with PWM frequency. This buffer exhibits the same circuit complexity of the 8 Bit predecessor, but the software is far more complex. In any case a complete software package is now ready for uploading.
5. To give an idea of the application range made possible by these new devices, I have prepared the following digital sensor list, by no means complete and expanding every day.
- Sandbox C02 Sensor.
- Many sensors for different gases.
- BMP082 Barometric Pressure Sensor.
- BMP280 Baro - Altimeter Sensor.
- TMP 007 - Infrared Temperature Therometer/Sensor.
- TCA 9548A I2C 1 to 8 Multiplexer.
- ST CN75 Ultra Precision Temperature Sensor.
- MCP23017 16 Bit I2C Serial Expander.
6. The buffers will keep the flexibility and versatility of the Picolog software, while at the same time exploiting the technical advantages of the new (and very affordable!) digital sensors.