The following blog post details the series of steps which should be followed before starting an experiment with ASI’s 600A Digital Controller.
1. Turn on the apparatus. TEC controller, length controller and force transducer electronics.
2. Turn on the PC, log in, and start the ASI600A program
Steps 3-4 only need to be performed for first time operation or if a different length controller or force transducer are to be used. If you have previously setup your instruments, skip to step 5.
3. Click on the Calibrate Menu heading.
4. Select Models Attached. Click the button next to the appropriate length controller and force transducer. When the arrow points up the model beside it is selected. This sets the default calibration values for length and force to the settings that correspond to the selected instruments. If you are using instruments that are not listed on the Models Attached screen then make sure you perform the Length and Force calibrations before proceeding to step 5. If you are using a dual-mode lever system (measures and controls both length and force) select the model number under Lever Systems and then select “None” under Force Transducer. Exit the Models Attached screen by clicking on OK.
Note: It is best practice that you perform a proper calibration of your length controller and force transducer post shipping and routinely thereafter. Refer to the manual for calibration instructions and follow our blog to see an upcoming post on calibrating ASI instruments with 600A.
Fig 1. Models attached window showing 300C attached with Force Transducer set to none
Prior to each experiment the following steps should be performed:
5. Click on the Setup Menu heading and then click on Open. The Setup window will open. You will note the Setup window is divided into five sections, Set Reference Length, Fiber Cross Section, Other Parameters, Set Zero Load and Notes.
Fig 2. Setup window
6. In the Set Reference Length section press the Zero Lout button and then enter the current muscle tissue length in the Reference Length text box. Now press the Record Lin button. After pressing the Record Lin button the program will sample the current Length In value and display this value, in mV, in the Lin – Length In text box. At the same time the program will display the reference length in the Lref – Ref. Length text box.
Note: After setting the reference length do not adjust the Zero Offset potentiometer control on the front of the length controller or the X stage controls that affect the overall tissue length. If you do, you will create a length offset between the actual position and the position that the computer reports. This offset can result in incorrect data being recorded and the system not controlling to the desired length, force or sarcomere length. If you change the Length Offset potentiometer on the Length Controller or the X stage position then you must perform step 6 again.
7. The lower half of the Set Reference Length section allows you to enter the initial length (Lo) and the fiber length (Lf). You have the option of manually entering Lo and Lf or having the program set them automatically. Click on the Lo=Lref button to set Lo equal to Lref. Lo is used for plotting length in terms of L/Lo but it is also used in test protocols for controlling length. If you want to work in units of fiber lengths then either enter the fiber length (Lf) or click on the Lf=Lo button to set them equal.
Note: Do not set Lo to zero. Unexpected operation of the length controller can result from improperly setting the Lo value. Lo must always be set to a positive, nonzero value (the initial length of your tissue). This value is used in length control functions and therefore if it is set incorrectly unexpected movement can occur. Some researchers have set Lo to zero to make the 600A program operate in relative length mode. We don’t recommend this, instead use the new relative length and force command structure in your protocols. Please refer to the manual for further information.
8. In the Fiber Cross Section area of the Setup window the fiber cross section is set by first choosing the type of cross section: circular, rectangular or elliptical and then entering the dimensions corresponding to the type of cross section you selected. The program will automatically calculate the Effective Diameter (Do). Do is the diameter of a circular cross section that has the same cross sectional area as the tissue.
9. The Other Parameters section allows you to set the initial sarcomere length (SLo) if desired and the maximum tension the muscle can develop (Fmax). SLo and Fmax are used for plotting normalized sarcomere length and force (SL/SLo and F/Fmax). Both SLo and Fmax can also be used in protocol control functions. For this reason it is important that these parameters be positive and non-zero. If SLo and Fmax are not known then enter 1.0 for each of these parameters, do not set either of them to zero.
10. Near the bottom of the Setup window is the Set Zero Load section. Set the muscle to the desired baseline force and then press the Record Fin button. This will record the current force and display this value, in mV, in the Fin – Force in text box. As the user you can choose what to use as the zero force, options include but are not limited to:
a. Force before attaching the muscle tissue to the force transducer with the force transducer hook in air.
b. Force before attaching the muscle tissue to the force transducer with the force transducer hook in liquid.
c. Force with the tissue attached to the hook but with the muscle slack.
d. Force with the muscle set to Lo.
e. Force with SL set to a particular value.
f. Regardless of which option you choose after pressing the Record Fin button you will note that the force is set to 0 mN. The Set Zero Load function is similar to Set Reference Length in that it provides a datum to the computer for force control and reporting.
11. The last section is the Notes section at the bottom of the window. If desired enter comments in the Notes section and these comments will be stored in all data files.
12. Either leave the Setup window open or close it by using the X control in the top right corner.
If you intend to use force control or SL control in your experiment you will need to setup the Force and SL control parameters before starting each experiment. This is done through the Force and SL control window. Please see the upcoming post on setting up these parameters on the Force and SL control window.
Please follow our blog to see further posts regarding the operation of our 600A software. Also, if you have any requests regarding a blog post please do not hesitate to contact us.