ANY-maze Help > I/O devices supported by ANY-maze > Legacy I/O devices > The ANY-maze interface (AMi) > Installing and configuring AMi > Configuring AMi > AMi configuration - Analogue inputs

AMi configuration - Analogue inputs

To access the AMi configuration window, select your AMi device in the list on the left side of the I/O page and then click the button to Configure this device in the ribbon bar.

Introduction

AMi includes 4 analogue inputs which can be used to sample signals up to 16V at rates of up to 1KHz. The exact input range and sampling rate to use are specified on the Analogue inputs page of the AMi configuration window.

Figure 1. The 'Analogue inputs' page of the AMi configuration window.

Details

Input range

The AMi analogue inputs are 10-bit, which means that the voltage applied to them will be converted to a digital value with 1024 possible levels. For example, if the input range is set to 0 - 1.024V then AMi would convert the input voltage to a number which would have a resolution of 1.024 / 1024 volts, i.e. 1mV. On the other hand, if the input range was set to 0 - 16.384V then input voltage would be converted to a number with a resolution of 16.384 / 1024 volts, i.e. 16mV. In practical terms, what this means is that in the first case, ANY-maze would be able to tell the difference between a 19mV and a 20mV input, whereas in the second case it wouldn't (they'd both be considered to be 16mV).

As can be seen, the wider the range of input voltages that the input can accept, the lower the resolution, - so you will usually want to adjust the input range depending on the voltage you will be sampling. For example, if you will be reading data from a gas analysis device which outputs a signal from 0 to 2V (perhaps representing the level of CO2) then you could use any range with a maximum value greater than 2V, but you'd probably choose to use the range 0-2.048V as that would provide the best resolution while still being able to convert the maximum value of the input. Incidentally, if you used a range of 0-1.024V, for example, and the input was at 2V then your AMi would not be damaged, but the input would just be reported as being 1.024V (i.e. the maximum value).

AMi has six input ranges, and you should select the lowest one that still covers your expected range of input voltages.

Sampling rate

The sampling rate is how often AMi will read the voltage at the input. In the previous section, I used an example of a gas analysis device which outputs a voltage proportional to the level of CO2 at its sensor. CO2 levels are probably not going to change very quickly, and so if you were to read the voltage 10 times per second, you'd probably find that it doesn't change much between each reading. On the other hand, you might have another device which is generating a voltage representing an animal's ECG. This would be changing very quickly and you'd need to read perhaps 200 times per second, or more, so as not miss any of the changes.

This might make you think that you should just always read an input very fast, so that you'll never miss anything, but in the case of the CO2 levels you'd just be recording a lot of data for no good reason and this would make your experiment file unnecessarily large.

The frequency at which AMi reads an input is called it's sampling rate and you should set it to the lowest value you can, without compromising the data you want to measure; but err on high side - recording too much, while best avoided, is still better than recording too little.

The AMi analogue inputs support sampling rates from 1 to 1000 samples per second.

ANY-maze help topic T1157