Introduction

The unit is compact and lightweight
Dimensions:	67 x 25 x 8mm (2.6 x 1.0 x 0.3”)
Weight:	12g (0.42oz)
Input Voltage:	4-15V
Power Requirement:	140mA (display active), 30mA (display blank) @ 5V
Memory:	4090 samples (sample rate adjustable)
Resolution:	(1’)
Manufacturer:	Hexpert Systems
Available From:	Matt Woolsey

I’ve been flying electric-powered sailplanes for a number of years now, and maximum altitude would be a very handy measurement for testing power systems in these models. To that end, I picked up an altimeter watch a couple of years ago in order to record my peak altitude. The watch is bulky and weighs enough that placement in the fuselage was somewhat difficult, but it was handy nonetheless.

Aerial Photography is another aspect of this hobby where altitude readings are desirable. Besides ending those “mine’s higher than yours” debates, it’s useful to know at what altitude various shots were taken. A simple peak-altitude recording device is not all that useful in these applications.

Enter the latest generation of recording altimeters, the ZLog from Matt Woolsey and Hexpert Systems...You can find out how high your flight went with the onboard display. It also records the complete flight for analysis on your PC with either a serial or USB interface.

What’s in the box?

The package I received included the ZLog unit, a CD with the manual and application software, and a USB cable. The latest application and manual can also be downloaded from Hexpert Systems website.

What's in the box

The manual is comprehensive – covering everything from basic setup to firmware upgrades. The specifications are listed here too, which is the first page I went looking for to determine the weight, operating voltage range, and current draw of the unit. The manual may be downloaded from the web site listed above, and some of the key specifications are provided in the table above. Note the current requirements vary based on supply voltage – the higher the voltage, the lower the current. It is also very convenient that the user can blank the display to further reduce power required.

The unit is compact and lightweight Layout of the components

As can be seen, the unit is lightweight and, although longer than other units I’ve seen, it is very thin, and its profile made it easy to fit into some very small models, including my hand-launch.

Installs in most models with ease.

A nice feature is the inclusion of a “port replicator” – if you are forced to plug the ZLog in to a channel that is already in use (i.e. in a 4-channel model with a 4-channel receiver), you can plug your servo in to the ZLog unit itself. Note that the wires are very lightweight and you should not use this connection for your ESC, for example, which would require the total current for all servos to pass through these wires. A small compromise, however, to ensure the overall weight of the unit remains low!

The on-board display is what really differentiates this unit from others. It is great to have the ability to determine your peak altitude for a flight immediately upon landing. It also allows you to configure the various parameters in conjunction with the two switches mounted on the board.

Programming chart

Another great feature allows you to mark data points throughout the flight – useful for marking various points in the flight, and a great way to enhance those aerial photography sorties, to determine the altitude of every picture taken (by triggering the camera and the ZLog from the same servo channel).

The resolution of the ZLog can be limited by setting the recording units in feet, yards or meters – in feet, you can move the unit from your desk to the top of your monitor, for example, and see the change on the display. You can also change the recording interval to suit your needs – as fast as 10 samples per second (with the latest 2.6 firmware), as slow as one sample every few hours (now that would require a long flight!)

Software application

The Connect/Download screen

The software is intuitive, and presents information in four logical tabs. The first is a basic info screen marked “Connect/Download” which, not surprisingly, allows you to connect to the ZLog unit and download the stored data. It also allows you to erase all data from the device. In order to download the stored data, you simply connect the unit, then click on the “connect” button to establish a connection. You then download the information which lets you know how many data sets were recorded. Finally, select each data source in turn, download, and save from the Recorded Data screen. Note that when using the serial interface, the unit must be powered by an external battery (a receiver pack, for example). The USB interface has the ability to power the unit directly.

The Configure screen

The second is a “Configure” screen where all the parameters concerning operation of the device may be set. The screen is self-explanatory, but note the additional parameters that can only be set through the PC application – the unit may be calibrated from a known altitude reference (keep in mind changes in barometric pressure will cause this value to drift), and the auto-start/auto-stop time and altitude values. I personally find the auto-start feature very useful – I have the ZLog installed in the fuselage of my hand-launch glider, and it starts recording automatically 10 seconds after I power up the model. The configuration can be read from, written to, or restored to factory default settings from this screen. Another useful feature appears when you update the configuration, or erase the data, from the PC application. The display flashes “CFG” or “ERAS” so you can be sure the action was performed successfully. Finally, note that the firmware for the unit may be updated from this screen. This means the end-user can take advantage of software upgrades as soon as they are available, by downloading from Hexpert Systems’ support file web site, and upgrading the unit through this application.

The Recorded Data screen

The third tab is the “meat” of the product - review the recorded data. The screen is packed with buttons and information, but it’s clearly presented – simple manipulation tools to zoom, crop and pan the display are located in the top corners. A very handy feature is that by default, the cursor will zoom on any selected area.

Draw a box around the area of interest ... and the display updates to show just that section.

You can also measure the rate of climb (or descent) by simply dragging the mouse between two data points. The displayed rate of climb is in the currently selected units of measure – i.e. feet per second in my data.

Drag the mouse across the data points ... and the rate of climb (or descent) is marked.

The Fix Drift and Fix Offset buttons correct for barometric pressure drift and data offset. The data points recorded using an external trigger (which I utilized in the sample data to mark when I was taking pictures) may be exported to a simple text file.

Exported data points

You have the ability to customize the graph display on the screen, by editing the various axis, colors, etc.

Various paramaters may be adjusted here. Scale of the graph may be entered manually.

Data may be saved to disk in comma-separated format, and previously saved data may be loaded in from here too. The exported data may then be loaded into Microsoft Excel for further analysis or manipulation.

Data can be saved in BMP or JPG format, as well as printed

The current displayed data may be exported in either BMP or JPEG format, in any size desired (which controls the resolution of the exported graph) and optionally in color or black and white. Colors and parameters such as axis labels, scale, background image, etc. are all preserved from the current settings in the displayed data. The same graph may be printed directly from this screen.

The About screen

The last tab simply shows the information about the application – version, build date, as well as email and web site information for contacting the manufacturer. A link to the PDF manual file, if downloaded and stored in the same directory as the application, is also provided.

Conclusion

I love this gadget! It stays installed in my hand-launch glider, in anticipation of the day when I’ll have it “specked out” in a thermal, or get that super-long flight I’ll want to brag about. The only time I remove it is when I take aerial pictures, or want to test climb rate in a powered sailplane (or accurately record my flights and thermal performance for competition purposes.)

A great way to see how my launches are improving! An extended flight with my Gambler.

The basic unit can record 4090 data points for the standard memory, which translates into about an hour of flying at 1 second/sample. An optional memory upgrade is available for $5, which will allow for four times as much data to be collected (16378 data points).

Matthew is very active on our RCGroups discussion forums, and maintains a thread in support of this product there. This a wonderful product that almost every modeler will want to own!