Measuring Resistance With The Hydra

Using The Hydra To Measure Voltage

Why Use The Hydra DAU?

The Hydra Data Acquisition Unit - the DAU - is an IEEE-488 instrument that can be used for measurements of:

Temperature (^oC) x DC Voltage
AC Voltage
Resistance
Frequency

Here is what the instrument looks like. It has two sets of data input terminals at the lower right on the front panel, and another twenty sets of terminals that have been wired to a connector on the top left of the unit. It has an LED message panel on the right, and measurements are displayed there normally, but not when you take a reading using a computer program - a subject of another lesson.

Advantages of the Hydra include the following.

It can measure a number of different variables.
It features 21 measurement channels.
The Hydra DAU can be controlled using C programs or Visual Basic, and programming is not difficult.

Your learning goals for this lesson about the Fluke Hydra Data Acquisition Unit (DAU) are the following.

Given a requirement for a DC voltage measurement with the Hydra
Be able to set up the Hydra to measure DC voltage.

How Do You Use The Hydra DAU?

You can take measurements of voltage, temperature, frequency and resistance with the Hydra. It's much like a voltmeter of DMM (Digital Multimeter) when you use it in the manual mode. In this section we'll run you through how you use the instrument in that mode.

There is a sequence of steps that will ensure that the instrument is ready for a measurement.

Turn the Hydra on. That's not a facetious statement. And be sure it's plugged in. The Hydra will go through a start-up sequence (green lights will flash on the front panel) and it will come up in the mode it was last in before being turned off.

The Hydra may come up in a monitor mode. That means it takes repetitive measurements - which might be voltage, temperature, etc. on a particular channel - and it will start that operation. If it comes up in monitor mode - and you will know that by it's efforts to take measurements repetitively - depress the white MON key in the lower right corner of the front control panel.

While not in the monitor mode, depress the FUNC key at the top left of the front control panel. You should see the words SET FUNC in small green illuminated letters on the display panel.

Now you can cycle through the different functions - the operations the Hydra will perform - by using the arrow keys on the front control panel.

Cycle through to get DC V showing and depress the ENTER key to set the function to measure resistance. If you want to make another kind of measurement you would choose that measurement at this point.

Now, select the channel on which you want to meaure the voltage by using the up and down arrow keys. The left and right arrow keys will not change anything. Normally, you would use Channel 0 - the front panel terminals.

After you depress the ENTER key you can either set the scale (e.g. 10 Kohms, etc.) or you can let the instrument autoscale itself - choosing the scale on its own. If you want the instrument to autoscale, choose AUTO using the up-down arrow keys. (The left-right arrow keys won't work here!)

At this point the instrument is configured to take measurements. If you want the instrument to take measurements over and over again, depress the MON key to put the instrument into the monitor mode. It then monitors whatever it is connected to by measuring at a few second interval. In student labs this is the usual mode of operation.

Measurements will be taken from the front panel connections - the red and black terminals.