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tension.md

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Tension Module Documentation

sMDT.data.tension is a module that contains the derived classes of Station and Record for use with the Tension Station.

This module has two main classes, the Tension object, and the TensionRecord object. The Tension object is a Station that holds a list of TensionRecords.

Tension Station Object

Member Functions Parameters Return Description
Constructor None None Constructs the tension station object
passed_first_tension() None Bool Returns true if the tension station has any passing tension records.
passed_second_tension() None Bool Returns true if the tension station has a pair of passing tension records that were recorded at least a week apart.
status() None Status Returns Status.PASS if the tube has passed its second tension. If it has no records, or if the first passing record was less than two weeks ago, returns Status.INCOMPLETE. Otherwise, returns Status.FAIL
fail() None bool Returns True if this data indicates a failed tube. This is equivalent to status() == Status.FAIL.

TensionRecord Object

tension.TensionRecord is the Record object that stores a single instance of data from the tension station. It's mostly a data container, but provides useful functions for printing and fail testing.

Failure condition: A TensionRecord is considered a failure if tension is outside the range (335,365) g.

Member variables Units Description
tension g The calculated tension of the tube using the following equation $T = \frac{\pi L^2 d^2 f^2 \rho}{g}$. This calculation involves the tube's length, diameter of the wire, measured frequency, and density of the wire. The length used is 1605 mm in the calculation.
frequency Hz The frequency measured by vibrating the wire. Tension is calculated with this value.
date datetime the datetime object representing when this was recorded. By default, it's datetime.now() at the point of record creation
Member Functions Parameters Return Description
Constructor tension : float, frequency : float, date : datetime, user : string TensionRecord object Creates a record object with the specified data
__str__() None string Returns a string representation of the record
fail() None bool Returns True if this data indicates a failed record. See above for the failure condition.

Usage

See the Station documentation for more depth on how to use station objects.

from sMDT.data import tension
tStation = tension.Tension()                                                #instantiate tension station object
tStation.set_record(tension.TensionRecord(tension=350, frequency=3.2))      #add 3 TensionRecords to the tension station, nonsense values for frequency
tStation.set_record(tension.TensionRecord(raw_length=345, frequency=8))
tStation.set_record(tension.TensionRecord(raw_length=370, frequency=5))
print(tStation.get_record("first"))                                         #print the first TensionRecord, and whether the tube fails based on the last record.
print(tStation.status())                                                    #Print this tube's status.

should output

Tension: 350
Frequency: 3.2
Recorded on: [String representing datetime object of when the record was created]
Status.INCOMPLETE

This tube is incomplete because while it does not have two passing tensions that are two weeks apart, it's first passing test is within two weeks ago. (Unless it took a REALLY long time to run some of those lines)