Reading force measurement values from A&D’s LCCU-21 button load cell

A&D’s LCCU-21 USB subminiature button load cells are available in capacities ranging from 100 N to 1 kN. Their tiny size makes it easy to incorporate them into your own machinery or test equipment. They are connected to an A/D converter with a USB interface, enabling you to quickly build PC-based force measurement and data acquisition systems at a very affordable price.

A&D LCCU21N100 usb button load cell

LCCU21 device profile in Simple Data Logger

As an alternative to A&D’s free WinCT-DLC application, you can also use these load cells with the most recent release of our Simple Data Logger software (SDL v1.2.1). In this article, I’ll show you how to configure SDL to request data from the load cell in user-defined intervals (polling).

The LCCU-21 button load cell has two data transfer modes: continuous transfer of up to 100 values/s and a command/reply mode. Currently, only the second mode is supported by Simple Data Logger (continuous mode has to be started and stopped by sending special commands to the LCCU-21, which is something that will be available in a future version of SDL).

Force measurement using A&D’s LCCU-21 button load cell and Simple Data Logger

1. Download and install Simple Data Logger.

2. Go to the license tab and enter a license key (required for the polling function). You can purchase license keys from FastSpring through a completely automated process (including a “90 days” license for only US$5). You can also contact us if you require a free trial license or apply to become a reseller if you want to sell our software to your customers.

3. In the input tab, set the device to “A&D LCCU21”, then click on set default parameters for device. This will set all interface parameters for you. The only thing left to set is the (virtual) COM port which appeared on your PC after connecting the LCCU-21 to a USB port (see this PDF document for further information):
A&D LCCU-21 usb button load cell: configuration in input tab

5. Switch to the control tab, enable polling and set the timer to a value that makes sense for your application. Click on set default command for A&D LCCU21; this will automatically enter the “RLMV” command which will be sent to the USB button load to request measurement data:
Set default command for A&D LCCU-21 usb button load cell

6. Select a file in the output tab. Click on the set values button to automatically set the values below for your region so that you can easily open the CSV file in Excel later. If you want to record the time with milliseconds, choose the appropriate format from the drop down list or enter it manually:
CSV file format settings

7. Click on the start button in the start tab to connect to the LCCU-21 USB button load cell and to start sending the polling command. Commands and replies are shown in the event log. Captured measurement values appear in blue and are written to the CSV file. Click on stop to stop data acquisition and to close the file:
Data acquisition from A&D LCCU-21 usb button load cell

Notes on the LCCU-21 button load cell

  • I don’t have the LCCU21N100 I used for testing anymore, so if you have any questions about it, please contact A&D.
  • The product brochure (PDF) contains several creative application examples, including one where load is applied by pressing the button load cell with a finger. When I tried this, it worked, but not very well: I found that it is impossible to press only the load sensitive surface (though maybe that’s not an issue for people with smaller fingers). It is therefore advisable to “apply load to the load cell through a rigid surface” as stated in the user manual.

Further information

Interface description (RS-232) for A&D FX-i and FZ-i precision balances

A&D’s FX-i and FZ-i precision balances are equipped with a serial interface (RS-232) and can be easily connected to a computer for data transfer (if necessary with a converter from RS-232 to USB or to Ethernet). You can, of course, also connect other devices such as a serial printer, a data logger or a secondary display.

I recently tested all communication modes and their various settings in order to update the product description in our German scales shop. Since this took me a lot of time, I also translated my findings into English for publication on this blog.

I found that all commonly used communication modes (a.k.a. transfer modes, transmission modes) are supported and that they can often be fine-tuned in a way rarely possible with other balances. Concerning the data format, the FX-i and FZ-i balances support not only A&D’s standard format, but also several other formats which might make these scales suitable as a drop-in replacement for older Mettler Toledo or Sartorius balances. However, the more recent SICS protocol was not implemented.

The balances support a number of commands for bidirectional communication. Unfortunately, not all applications and settings are accessible via remote commands (for example, the limits for checkweighing cannot be set by a connected computer).

You can use any terminal software to test communication via the RS-232 interface (e.g. HTerm or PuTTY). For productive use, I recommend A&D’s free WinCT software or our Simple Data Logger software. The best integration can often be achieved by customizing your own software to communicate directly with the balance.

RS-232 interface and cable

FX-i and FZ-i balances have a built-in DE9M connector and require a straight (1:1) cable (not a null modem cable):
RS-232 interface on A&D FX-300i balance

Interface parameters

Default settings are highlighted in bold:

Baud rate: 600, 1200, 2400, 4800, 9600, 19200
Data bits: 7 bits or 8 bits
Parity: even, odd (for 7 data bits), none (for 8 data bits)
Stop bits: 1 bit
Data flow control (handshaking): none (RTS and CTS lines are connected internally but not used for actual flow control).

Data format

By default, the balances use the proven A&D format and transmit 17 ASCII characters for each weight value:

First line: number; second line: ASCII characters sent by the 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

As far as I know, the very first scale from A&D with a data interface already used the same format. This is very impressive, particularly when other manufacturers sometimes change the data format between firmware updates or even between transmission modes.

As alternatives to the A&D format, 5 further data formats can be used. The user manual (PDF) contains a detailed description in chapter 10-6.

Communication modes

The corresponding setting in the menu of the balance is indicated in [square brackets].

  1. Key mode: The weight is transmitted when the PRINT button on the balance is pressed.
    • Mode A: Only when the weight is stable [dout / Prt 0].
    • Mode B: Immediate transmission (stable and unstable weight) [dout / Prt 4].
    • Mode C: The balance waits until the weight has stabilized and then transmits it [dout / Prt 5].
  2. Auto-print: The weight is automatically transmitted after stabilization.
    • Mode A: Return to zero is required before next transmission [dout / Prt 1]. You can set which range around zero counts as “zero” (10, 100 or 1000 digits) [dout / AP-b]. You can also specify whether only positive, negative or all values should be transmitted [dout /AP-P].
    • Mode B: No return to zero is required before the next transmission [dout / Prt 2]. You can set the required difference from the last stable value (10, 100 or 1000 digits) [dout / AP-b]. You can also specify whether lower, higher or all values should be transmitted (compared to the last stable value) [dout /AP-P].
  3. Stream mode: Continuous transmission of 5, 10 or 20 values/s [dout / Prt 3]. The frequency is determined by the display refresh rate [bASFnc / SPd]. This mode is not suitable if you connected a printer or hardware data logger to the balance, but it is required if you want to use an external display. Our data logger software can also easily handle this number of values per second.
  4. Interval mode: Transmission of a value every 2, 5, 10, 30 or 60 seconds or every 2, 5, or 10 minutes [dout / Prt 6].
  5. Command mode: The balance responds to commands received over the interface (bi-directional communication). Available in all modes, see commands below.

In mode 1, 2 and 4, the display blinks to signal that the weight has been transmitted.

Supported commands

“Q” is used to get the weight immediately, while “S” is used to get the next stable weight. All commands must be terminated with carriage return and line feed:

No.:  1  2  3
ASCII: Q CR LF
Hex: 51 OD 0A

Complete list of commands (in alphabetical order):

?ID Requests the balance ID (can be set through the menu).
?PT Requests the pre-tare value (which has been set using the PT command).
?SN Requests the balance’s serial number.
?TN Request the balance’s model name.
C Cancels the S or SIR command.
CAL Same as pressing the CAL button.
<ESC>P Same as the “S” command. <ESC> is the escape control character (1Bh). Compatible to Sartorius SBI and older Sartorius balances.
<ESC>T Same as pressing the RE-ZERO button.
EXC Calibration using an external weight (only for FZ-i).
Q Requests the weight data immediately.
OFF Turns the balance off.
ON Turns the balance on.
P Same as the ON:OFF button (“P” = power?).
PRT Same as pressing the PRINT key.
PT Sets a tare value, PT:xxx.x g. The unit must be transmitted using A&D’s format (3 characters, right-justified, padded with spaces).
R Same as pressing the RE-ZERO key.
S Request the stabilized weight.
SI Same as “Q” (compatible to older Mettler-Toledo balances).
SIR Switch to stream mode (continuous transmission).
SMP Same as pressing the SAMPLE key
T Tares the balance.
U Same as pressing the MODE key.
Z Same as pressing the RE-ZERO key.

Other settings affecting RS-232 data transmission

You can set the balance to acknowledge valid commands with the ACK control character (06h) and to reply to invalid with “EC” and an error number [SiF / ErCd]. The manual contains detailed information and examples in chapter 16-2.

The terminator can be changed from carriage return and line feed (0Dh 0Ah) to carriage return (0Dh) [SiF / CrLf]. This affects both the output and the input (commands).

It’s also possible to change the decimal point to a comma [bASFnc / Pnt].

The balance can re-zero (tare) itself after sending the weight, which is useful during formulation [dout / Ar-d].

FZ-i balances are equipped with an internal clock and calendar and can output the time, date or time and date [bASFnc / dout / S-td]. According to the manual, this only works when outputting GLP data and not with individual weight values (I will test this later this week). This information can be added to the weight data [dout / S-td].

You can use the animal weighing application to calculate an average weight and automatically output it (as shown in this short video). Statistical calculation mode can output numbered individual weight values and summarized statistical data.

You’ll find further settings in a function table in the user manual (chapter 10).

Further information

 

Ohaus Ranger 7000: can a scale simplify complex weighing applications?

“Simplifying even the most complex industrial applications” is the claim that Ohaus makes in their data sheet. Is it justified? After spending some time trying out the different functions of this scale, I believe that yes, it is.

The key to understanding the power of the Ohaus Ranger 7000 scales are the 10 application modes:

  • Weighing: Determine the weight of items (no surprise here). A statistics feature can be used in weighing mode to calculate statistical data.
  • Counting: Count parts of uniform weight. Auto-optimization recalculates the average piece weight as the number of pieces is increased.
  • Check weighing and check counting: Compare the weight or count of a sample against target limits. Connect with discrete I/O option kit to use external check lights.
  • Formulation: For compounding and recipe making. Compensation can be used in case a component is overfilled (outside the tolerance).
  • Percent weighing: Measure the weight of a sample displayed as a percentage of a pre-established reference weight.
  • Filling: Fill a container to a target weight. Progress bar displays filling status. Connect with discrete I/O option kit to control a semi-automatic filling system.
  • Dynamic weighing: Weigh an unstable load. Scale takes an average of weights over a period of time. Can also be used as a display hold function.
  • Density Determination: Determine density of solids.
  • Differential weighing: Calculate the difference between sample weights and initial weights.
  • Sieve analysis: Used to assess the particle size distribution (also called gradation) of a granular material.

Each application is displayed differently on the 4.3 inch color screen. Compare, for instance, the display in weighing mode to check counting mode:

Weighing application on Ohaus Ranger 7000 scale

Weighing

Check counting application on Ohaus Ranger 7000 scale

Check counting

The applications are not limited to different presentations:

  • Five physical smart buttons below the display take on different functions depending on the application.
  • All settings relevant to the current application can be accessed easily by pressing the settings button.
  • The internal library allows you to save application specific data for commonly used items (e.g. the target weight and tolerance for check weighing, the average piece weight in counting mode or the set points in filling mode). The scale can be connected to a bar code reader to simplify recalling data from the library.
  • An optional I/O kit with four outputs (relais) and 2 inputs can be used to integrate the scale with external devices. The functionality is again dependent on the application mode. One of our customers has used the filling application with the I/O kit to build filling machines controlled entirely by a Ranger 7000 scale.

Therefore, as long as your application is supported by the scale, it does an excellent job at simplifying many tasks.