Review: AEMC OX 7104-C handheld oscilloscope, part 3/3
Read Part 1 and Part 2 of this review
This installment covers the OX 7104-C's DMM and recorder features, and its SX-Metro PC software
To use the DMM, you must change the probe adapter, which takes away one or more of the four scope channels, but makes for a versatile instrument. You can use any or all channels as oscilloscope or DMM inputs.
DMM functions are VDC, VAC, ohms, component test, Pt100 RTD (temperature), and capacitance. I used a DMM channel to measure a 16 V source. The Vertical menu lets you select DMM range and coupling. Double-tapping the channel’s DMM display should bring up the vertical settings menu, but it doesn’t.
While in DMM mode, the instrument has a recorder that displays history of recent measurements. You can set it to operate like a chart recorder where screen fills them and drops the oldest measurement or stops measuring when the screen fills. The recorder function works for recording slow-moving signals such as temperature. I used a 100 mHz (0.1 Hz) ramp signal from a function generator to evaluate the recorder feature. It has an interesting fault-detection mode that lets you set up ten triggered acquisition based on levels greater then, less than, equal to etc.
AEMC is the only of the four handheld oscilloscope makers to include a harmonic analyzer. It’s designed for power-quality analysis and covers 40 Hz to 450 Hz. At low voltage levels, I was able to get reliable results to 5 kHz. I tested with a sine wave and a square wave, seeing only the fundaments of a sine wave and only odd harmonics of the square wave.
The harmonic analyzer display shows each harmonic to the 30th with a check box under each harmonic. Tapping the box lets you display amplitude and phase information for that harmonic. The screen also displays RMS amplitude and total-harmonic distortion on the signal.
PC Software
AEMC’s SX-Metro software lets you import data from the OX 7104C and operate the oscilloscope (in scope mode) remotely. I used RS-232 first, and the PC quickly recognized the oscilloscope. Not so with the optional Ethernet link. I had to go into the Options menu in SX-Metro software to change the IP address to match that of scope. I kept getting communication error on PC, so I returned to RS-232 to evaluate the software.
With the SX-Metro software running over the RS-232 link, I tried saving a screen as a GIF or BMP file to then download to the PC, but found it difficult. The oscilloscope’s file manager is difficult to learn. I needed several tries to understand its operation.
I found the communication cable connectors difficult to insert. You must press the connector’s release button to insert it into the socket and still you must jiggle the connector to get it in. You could break the clips if you push too hard.
Overall, the AEMC OC 7401C is a powerful handheld instrument. Its bandwidth and resolution make it an alternative to some bench scopes. Its ability to mix and match oscilloscope and DMM inputs and its four channels are unique. It has a few quirks, particularly when saving files for PC downloading.
