Making an electronic hive scale can be harder than you think
Hive scales for use by beekeepers are a niche market; moreover, they must meet a number of special requirements, such as:
Must withstand long-term outdoor use (protection against rain, moisture/dust, very low and high temperatures, possibly theft/vandalism, wild animals etc.).
Must weigh accurately under challenging conditions (temperature fluctuations, vibrations caused by wind).
Must support a heavy load over a long period of time while still registering small weight changes.
Must be able to transmit weight data (often over long distances).
Must have low power consumption (for off-grid installations).
It is therefore unsurprising that no major scale manufacturer offers a hive scale and that commercially available scales from specialized manufacturers can be quite expensive.
List of hive scales available in Europe
The following list contains all beehive scales available in Europe that we currently know of (both commercial and open source / DIY projects). Websites with descriptions in English and with recent updates were highlighted:
It is a compact device designed to be connected to scales and balances made by A&D via their RS-232 interface. It stores the weight and – if required – a sequential number and the date/time. After weighing, it is connected to a USB port on a computer (just like a flash drive) to access the data:
The CSV file created by the AD-1688 can be opened in applications such as Excel by simply double-clicking on it. The weight will appear as a number in its own column, ready for further processing.
Does the data logger work with scales from other manufacturers?
Sometimes, but it almost never works as well as with scales from A&D. In our tests, the following problems occurred.
Connectors and pinout
Connectors of the cables included with the AD-1688 weighing data logger
The data logger comes with suitable cables for (almost) all scales and balances made by A&D. On a DE9 connector (often erroneously called DB9), it uses pins 2 (RxD), 5 (GND) and 6 (DSR), though the latter is not strictly necessary. To connect to scales from other manufacturers, you may need adapters such as “gender changers” or null modem adapters, or you may need to make a special cable:
Please do not assume that the pinout is compatible just because the connector can be plugged in on your scale!
Possible damage
Some scales use pins of the RS-232 port for other purposes, e.g. for powering peripherals such as check weighing signal lights. These pins must not be connected to the AD-1688!
Power supply via the RS-232 interface
The AD-1688 gets its power from the scale it is connected to (or the USB port when connected to a computer). RS-232 voltage levels are clearly defined in the RS-232 standard. Nevertheless, the “RS-232” interface of some scales does not supply the voltage required to operate the AD-1688. On a Kern DE parcel scale, for example, the data logger did not turn on at all, even though the pinout matched:
AD-1688 weighing data logger conencted to a Kern DE parcel scale
Further analysis revealed that this scale did not contain an RS-232 transceiver and that logic one (“mark”) was sent as 0 V (instead of −15 to −3 V).
Interface parameters
The settings for baud rate, number of data bits and parity must match on the scale and on the data logger, otherwise the AD-1688 won’t be able to read the incoming data correctly.
When using the data logger with scales from A&D, you do not have to worry about this: Almost all A&D weighing instruments use 2400 bps, 7 data bits, parity “even”. This is also the default setting of the AD-1688.
For scales made by other manufacturers you will have to change the interface parameters either on the scale or on the data logger. The AD-1688 supports the following settings:
Bit rate: 600, 1200, 2400, 4800, 9600, 19200.
Data bits/parity: 7 even, 7 odd, 8 none.
Data format
The data logger expects all data to be sent as ASCII in A&D’s standard format:
First line: byte number; second line: ASCII character sent by an A&D balance; third line: hexadecimal value
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
S
T
,
+
0
0
4
5
6
.
8
9
g
CR
LF
53
54
2C
2B
30
30
34
35
36
2E
38
39
20
20
67
0D
0A
Only a very small number of scales made by other manufacturers support this exact format. If your scale sends data in a different format, two problems may occur:
Unless each line is terminated with carriage return and line feed, the AD-1688 won’t record it.
Even if this is the case, the numeric value of the weight will not be separated from the unit (and other characters sent by the scale).
You can generally solve the second issue by using the import wizard of your spreadsheet application. With Excel, the easiest way to open the file in the import wizard is to rename it from .CSV to .TXT.
Many scales send several line breaks after the weight (for the paper feed of a serial printer). This causes the data logger to create empty rows not containing any data. If you cannot modify the line feed configuration of your scale, you can instead increase the “Line” setting of the AD-1688 to combine several lines into one row.
This will result in empty columns (see example file above), which is much better than empty rows. However, the maximum is 7 lines. Beyond that, data will spill into the next row.
Decimal point or comma
The AD-1688 data logger cannot convert between a decimal point and comma. If you’re in a country which uses a decimal comma, this again means that you will have to use the import wizard of your spreadsheet app to correctly format the weight as a number.
Note: A&D scales let you choose whether the weight should be sent with a point or comma (e.g. “12.34″ or “12,34″) and therefore do not have this problem. You only have to ensure that the “dP” setting on the data logger matches the decimal separator used by your scale.
Transmission mode
Most scales have a “print” or “data” button to send a single weight reading to a connected device. However, this is not always the case. Some scales send the weight continuously with several values per second. This would quickly fill the memory of the AD-1688. You can mitigate this by using the “Rec” setting so that data is only stored at certain intervals, but this is far from ideal for most applications.
Other scales use bi-directional protocols (very common with point-of-sale scales):
Example: NCI POS protocol
Such scales can definitely not be used with the AD-1688 weighing data logger as it can only passively record incoming data. It is unable to send requests to the connected scale (see pinout above, there is no transmit pin).
Intended use according to A&D
Finally, the manual (PDF) clearly states that the AD-1688 is designed to be connected to “balances and scales with an RS-232C connector manufactured by A&D“. It was never intended to be used with weighing instruments made by other manufacturers. Given the many pitfalls described here, this is an understandable decision.
Conclusion
The trouble-free operation of the AD-1688 weighing data logger is only guaranteed with compatible scales from A&D.
On scales from other manufacturers, the AD-1688 may work, but there are many potential problems that can cost you a lot of time. Even in the best case, the resulting CSV file will often not be fully comma-separated due to differences in the data format and will require further processing.
If your scale is not made by A&D, consider connecting it to a PC for data acquisition. You can use our Simple Data Logger software, which is designed to work with scales from many different manufacturers.
Note: The information in this article is valid for firmware P1.10 of the AD-1688.
Links and further information about the AD-1688 weighing data logger
Defender 5000 scales can be equipped with a WiFi or wired Ethernet interface. The scale acts as a TCP server and your script establishes a connection as a TCP client. You can then use one of the supported commands to request the weight or simply wait for the scale to send the weight (e.g. when the operator presses the print button).
You can easily test this by using PuTTY in “raw” mode and connecting to the scale:
The WiFi dongle uses port 6060 (wired Ethernet: port 9761), the IP address is assigned via DHCP by default.IP (immediate print) command used to request the weight and reply sent by the scale (N: net weight, G: gross weight, T: tare weight).
<?php
error_reporting(E_ALL);
echo "TCP/IP Connection\n";
/* Ohaus Defender 5000 WLAN interface uses port 6060 by default, Ethernet interface uses port 9761 */
$service_port = 6060;
/* IP address of the scale, can be displayed/set in the menu */
$address = "192.168.0.195";
/* Create a TCP/IP socket. */
$socket = socket_create(AF_INET, SOCK_STREAM, SOL_TCP);
if ($socket === false) {
echo "socket_create() failed: reason: " . socket_strerror(socket_last_error()) . "\n";
} else {
echo "OK.\n";
}
echo "Attempting to connect to '$address' on port '$service_port'...";
$result = socket_connect($socket, $address, $service_port);
if ($result === false) {
echo "socket_connect() failed.\nReason: ($result) " . socket_strerror(socket_last_error($socket)) . "\n";
} else {
echo "OK.\n";
}
$in = "IP\r\n"; //IP command (Immediate Print) - supported commands depend on the manufacturer, model and LFT settings
$out = '';
echo "Sending command...";
socket_write($socket, $in, strlen($in));
echo "OK.\n";
echo "Reading response:\n\n";
while ($out = socket_read($socket, 2048)) {
echo $out;
}
echo "Closing socket...";
socket_close($socket);
echo "OK.\n\n";
It produced the following output:
You can modify the output template through the menu of the scale or by using the Ohaus Scale Mate software, e.g. to send just the net weight and date/time:
You’ll find a list of commands supported by the scale in the user manual. In the script, I used the IP (immediate print) command, which tells the scale to send the weight immediately (whether it is stable or not). This command is available on all newer Ohaus scales. One notable exception are legal-for-trade (LFT) models, which only support the P command (similar to pressing the print button) and in some cases the SP command (stable print, send weight as soon as it has stabilized). The Defender 5000 also supports many MT-SICS commands (which is the closest thing to a communication standard that the weighing industry currently has).
Please note that I’m not a PHP expert and that this is not a recommendation to use PHP. It is only supposed to be a very basic demonstration (as a potential customer asked me if it was possible to use PHP to communicate with the scale). Other programming languages such a C#, Java, JavaScript or Python may be more suitable. I’m frankly not even sure why the script works the way it does, as I would have expected it to fill the buffer (2048 bytes) before outputting any received data.
The header photo shows a Defender 5000 communication test case (a hard case with a built-in Defender 5000 indicator with all optional communication interfaces installed).
CECIP, the European weighing industry association, has launched a campaign to “to make the general public and businesses aware of the importance of reliable and accurate weighing”.
The CECIP campaign focusses on the impact of weighing in daily life and in the operations of businesses. Although businesses generally understand the need for weighing, it is not always understood what the impact of inaccurate weighing could be. Yet, it can impact the core business when weighing results are not correct. For production companies inaccurate weighing of ingredients or parts can harm the quality of the final products. This is not always clear and CECIP hopes more business will be conscious about the importance of reliable weighing and the consequences weighing accuracy can have on their operations.
Overall, the campaign aims at making consumers, users and buyers of weighing instruments understand that weighing is not just the value you see on the display of a scale, but a vital process that contributes to our world functioning smoothly.
As part of the campaign the key messages will be spread via social media, magazines and the dedicated website: www.worldwithweighing.com.
![How to perform a stable measurement with a microbalance [video]](https://www.digitalscalesblog.com/wp-content/uploads/2020/09/mikrowaage-bm-20.jpg)
