flintec_lpp (log - process - plot)

This crate compiles the following three binaries for logging, preprocessing, and plotting load time series.

1 flintec_log

CLI app to log load cells via Flintec DAD 141.1 digital amplifier with TCP-UTF8. The app allows automatic logging at rounded intervals of minutes or hours that are divisors of 1 day. Valid minutes intervals are 1, 2, 3, 5, 10, 15, 20, 30, and 60 minute(s). Valid hours intervals are 1, 2, 3, 6, 12, and 24 hour(s).

2 flintec_process

This CLI app processes the load time series with the following steps: 1. Read the logged load time series, replacing possible logging or parsing errors with NAN. 2. Optionally, set outliers to NAN (based on a user-defined range). 3. Fill the datatime gaps with NAN to have a continuous time series. 4. Now that all invalid or missing load values are set to NAN, apply a weighted moving average to fill and smooth the load time series. It uses a moving average with linear weights between the user-defined central weight (typically the max weight) and the side weight (typically the minimum weight). The width of the window can be adjusted by specifying the number of data points on each side. Constraints can be set to define when the missing information (number of load values or their cumulative associated weight) is too large to fill the NAN values. 5. The CLI app saves a new csv file compatible with flintec_plot.

Note, throughout the crate, load is used for the load cells data, while weight is used for the moving average.

3 flintec_plot

CLI app to plot the load time series saved by flintec_log as a svg file.

Documentation: rust_crate

Notes on the DAD141.1

General

Calibration: Zero (intercept) and Span (slope, span calibration)

See examples in the DAD manual and section 7.4 (pag. 34) in the DOP manual. * Zeroing with function 1.2 - CZ (gravimetric) or 1.3 - AZ (electronic), this associates the current measured voltage (mV/V) with the zero reading. * Set span_kg with function 2.1, set ROkgsum. * Set span_V, from the formula below, with function 2.3.

Calculate the span value (span_V)

spankg = ROkgsum = ROkg1 + ROkg2 + ... ROkg_n.

In our case, spankg = 20kN * 6 = 120 kN = 120 = 12,236.5921 kg. Put ROkg_sum in function 2.1.

ROV1 + ROV2 + ... + ROVn = ROVsum, in mV/V.

spanV = (Vsum / kgsum) * kgmax, in mV/V. In our case 12.00062 / 6 = 2.000103333 mV/V.

In our case, SPANV = 2.00032 + 2.00034 + 1.99979 + 2.00014 + 2.00011 + 1.99992 = 12.00062 mV/V. Put spanV in function 2.3.

Where: * ROV is the voltage output (mV/V) at the rated output (RO) from the calibration certificates. * ROkg is the rated output, always from calibration.

kg from mV

kg@x = (mV@x / (mV@RO * ExcitationVoltage)) * kg@RO

kg@RO = 2039.43 kg mv/V@RO ~ 2 mv/V ExcitationVoltage should be 5 V

Example, ~2040 kg should give 10mV (i.e., 2 mv/V * 5 V) Example, ~1020 kg should give 5mV (i.e., 2 mv/V * 5 V / 2) in general, 204 kg = 1 mV

Format

The app expects the 10-byte DAD format, with flexibility on the position of the decimal separator. The first two characters are the description of the value and are excluded from the parsing of the numerical load value. However, the raw string is also written into the csv file to avoid losing information on the type of reading and recover the values in case of parsing errors. Possible whitespace-property characters (Unicode standard) will be correctly trimmed and ignored.

Installation of the load cells and mounting modules

Mounting modules

Three types of mounting modules are used to obtain the correct degrees of freedom, matching the deformation of the system. 1. Fixed: No mobility, the modules fixes the system point in that position (0D freedom). 2. Bumper: Constrains the movement in one direction (1D freedom). 3. Free: It allows the movement in all the directions, within the load cell plane (2D freedom).

Alignment

Align the load cells considering the degrees of freedom of the mechanical deformation. In particular, pay attention to the fixed and bumper load cell, and their alignment with respect to the main deformation at the bumper. See figures are in the manuals.

Lubricant/Grease

It is used to protect the mobile parts of the mounting module during their movement (rocker pin and matching top surface). * Mettler Toledo manual: Loctite Anti Seize, Food Grade * Flintec: At Flintec use RENOLIT ST-80, by Fuchs. However, they provided a similar one already with the load cells.

Remote/SSH logging

Find ip and/or hostname

  1. find the ip address, e.g., ifconfig.
  2. find the hostname with host ipaddr_from_ifconfig.

Starting

  1. ssh to raspberry pi, ssh user@ip
  2. open tmux, tmux
  3. start the logging process, see ./compiled_binary --help
  4. detach the tmux session n from terminal with Ctrl+b then d, which returns [detached (from session n)]
  5. check if tmux session is still there with tmux ls, it should return n: 1 windows (created datetime 2), where datetime is of point 2
  6. close terminal/ssh connection, exit, it returns Connection to uset@ip closed

Check logging

  1. ssh to raspberry pi, ssh user@ip, as step 1 of starting
  2. find tmux session with tmux ls, as step 5 of starting
  3. attach the session with tmux attach -t n, where n is the number from starting step 4
  4. repeat steps 4, 5, 6 from starting

Copy the data

  1. open terminal and copy file from raspberry to laptop with scp, e.g., scp user@localhost:~/path/to/file/loadcells.log ./Desktop/

Close logging

  1. ssh to rapberry pi, ssh user@ip, as step 1 of starting
  2. find tmux session with tmux ls, as step 5 of starting
  3. close running logging with Ctrl+c, should return [exited]
  4. double check with tmux ls, should return no server running on ...

Additional information