If you’re working in the weighing industry, you’ve probably come across the GX16 connector:
This circular connector is named after its M16 thread and can have up to 8 pins. While it is frequently referred to as an “aviation connector”, I sincerely hope that it is not actually used in aircraft, as I’ve seen many of these connectors fail. Their tiny screws are prone to coming loose, which renders the strain relief useless. Then it’s only a matter of time before the cable is pulled too hard and the wires detach.
What does it take to make a reliable GX16 connector?
This is the Ohaus Catapult 5000 scale:
It uses an overmolded GX16 connector to connect the platform to the indicator:
We’ve sold hundreds of these scales and never had an issue with them that was caused by the connectors. This is due to the extensive work that Ohaus put into making them, as demonstrated by the photos below. Apologies for the photo quality, I didn’t take them in our photo studio and it shows.
The scales are equipped with an RS-232 interface and can be connected to a PC for data acquisition (if necessary via an adapter from RS-232 to USB). They are known as “Everest EK/EW compact balances” in the US.
Applications such as the following can be used to capture the weight:
EK-i and EW-i scales support the following transmission modes:
Prt 0 – stream mode: continuous transmission of weight with approx. 10 values/s,
Prt 1 – PRINT key (default setting): transmission when pressing the PRINT key on the scale,
Prt 2 – auto-print A (positive values only): automatic single transmission when the weight is stable (return to zero required before next transmission),
Prt 3 – auto-print B (positive and negative values): automatic single transmission when the weight is stable (return to zero required before next transmission),
Prt 4 – command mode only: request-response mode, the computer sends a command to the scale and it responds with the weight value.
The display flashes briefly (in Prt 1, 2 and 3) to confirm the data output.
Commands from a connected computer can be sent in all modes.
The PRINT key is active in all modes except Prt 4.
There is no interval mode. If you want to capture the weight in certain intervals (e.g every minute), you need a software that supports polling with a timer (or you could set the scale to stream mode and discard most values).
These data output modes can be found in the Func class of the scales’ menu:
Changing the transmission mode
Turn on the scale.
Press and hold the SAMPLE key until the scale displays “P-3.00” (or a similar value). The scale shows “Func” next.
Press the PRINT key to enter the function settings menu. The first setting “PoFF” is displayed.
Press the SAMPLE key 8 times to enter the “Prt” setting. By default, “Prt 1” is set.
Set “Prt” to the desired value by pressing the RE-ZERO key (see description above).
Confirm the setting with PRINT. The balance displays “End” briefly and then “CP Hi”.
Some of the scales from A&D’s EJ series (known as “Newton” in the U.S.) can be equipped with an optional density determination kit (EJ-13), as shown in this photo provided by A&D:
The stainless steel weighing pan supplied with the scale is removed when the density determination kit is installed. Instead, a pan stand and a special double pan are used to weigh samples in the air and in a liquid.
The problem: these two parts weigh just 38.5 g, while the stainless steel pan weighs about 55 g, a difference of 16.5 g. The manual states, “the range for power-on zero is within ±10% of the weighing capacity around the calibrated zero point.”
For the EJ-120 with a capacity of 120 g, this is only ±12 g, so we can expect a “-E” underload error when the scale is turned on. After a few seconds, it will display a negative value, which annoyingly cannot be zeroed with the RE-ZERO key.
The solution: perform a zero point calibration after installing the density determination kit (no calibration weight is required).
Note: If you have not yet purchased an EJ series scale, consider purchasing one with a higher capacity to avoid this problem.
EJ-120 scale zero point calibration
Open the calibration switch cover on the bottom of the scale:
Remove the stainless steel weighing pan and install the density determination kit as described in the manual:
Switch on the scale and wait until a value is displayed (this can take a few seconds):
Press and hold the calibration switch until the scale displays “CAL 0” (then release):
Confirm the zero point with the [PRINT] key. The scale displays “100.00” (the required calibration weight for the next step, which we will skip):
Press the [ON/OFF] key to switch off the scale.
If you now turn the scale on again, it will display “0.00 g” with the density determination kit installed.
Note: Clever readers may have noticed that the total zero range of 24 g (±12 g) exceeds the 16.5 g weight difference. Therefore, it is possible to perform a zero calibration at a point where the EJ-120 scale automatically zeroes either with the density determination kit or with the stainless steel pan installed. However, this might not work reliably for long because factors such as temperature changes affect the zero point (which is the reason that the zero range exists).