PRT Calc ~~~~~~~~~~ Platinum Resistance Thermometer Calculator ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ I. Introduction. II. Main menu. III. Manual calculation. IV. Automatic calculation. V. Valid keyboard inputs. VI. Small print. I PRT Calc ~~~~~~~~~~ PRT Calc is intended as an aid for anyone who uses platinum resistance thermometers. It will calculate the resistance of a PRT at any temperature within the specified range or will calculate the temperature if the resistance is known. PRT Calc can, therefore, be used by people calibrating or designing platinum resistance thermometers based on BS 1904, or people who wish to use PRT sensors directly into a DVM or bridge without any intervening electronics. The formulae used by PRT Calc were derived from the British Standard BS 1904 : 1984, for which full credit is acknowledged. The formulae should give no errors greater than the least significant digit in the BS tables, hence ensuring that any results obtained by this program can be considered to be correct for all practical purposes. (If anyone discovers any errors PLEASE let me know). II MAIN MENU ~~~~~~~~~~~ The main menu in PRT Calc is used, both to change the various options, such as temperature scale, and to initiate the different modes of operation. Menu items are selected by using the vertical curser controls to highlight the required item, or by pressing the appropriate number or function key. Once an option item has been selected, the option can be activated by pressing RETURN or changed by using the horizontal curser keys, or in some cases by pressing a letter key. Brief instructions are given at the bottom of the screen for each item. Details of each item are as follows. 1. Help This item invokes the Help mode and, basically, displays or prints these pages. 2. Exit to DOS Exits from PRT Calc to DOS or whatever shell is in use. 3. Manual calculation This starts the normal mode of operation in which the user inputs a temperature or resistance and PRT Calc calculates the other (depending on the setting of the direction option). 4. Automatic calculation This mode is more useful if the user wishes to create a mini table of results. (The original BS tables are obviously better if more than a few values are required.) PRT Calc prompts for a starting value, an end value and a step size. It then performs the required calculations automatically. It is advisable to enable the printer option before using this mode. 5. Change direction This is one of the option items, with just two options; temperature to resistance or vice verse. The default is temp > res. in which case the user inputs a temperature and PRT Calc calculates the corresponding resistance Either of the horizontal curser keys, or the RETURN key, just toggle between the two options. 6. Printer output This is another two option item; enabled or disabled. The default is disabled, in which case the results are displayed on the screen only. If this option is enabled then results are also output to a printer (assuming one is connected of course). 7. Select temperature scale This item has four options; C,F,K,R; (Celsius, Fahrenheit, Kelvin and Reaumer). The default is C. The horizontal curser keys scroll through the options, or the choice can be made directly by pressing the appropriate letter key. 8. Nominal resistance This item enables the user to enter the nominal resistance of the PRT (i.e. at 0 C). The default for this value is 100 ê, which is the normal Pt100 standard. There are few exceptions, such as some high temperature probes. III MANUAL CALCULATION ~~~~~~~~~~~~~~~~~~~~ To start manual calculation, highlight item 3 in the main menu and press RETURN, after changing any of the options if required. Manual calculation is the normal mode of operation for PRT Calc. It accepts any valid input entered via the keyboard and immediately displays the result. Firstly it displays a header showing the current settings of all the options and then prompts you for an input. If the input is valid (see section headed Valid Keyboard Inputs) it then displays both the input and the result in two columns. (The reason it redisplays the input is that it does so in a consistent, readable format, acting as a visual check on the input and tidying up the printout if enabled). If the printer option has been enabled then the header and both columns are also printed. If the input is invalid then a warning message is displayed (and printed). If the input is only just outside the valid range then a result is given along with a warning that the result is only approximate. When you have finished, or to change any of the options, press RETURN with no input. This returns you to the main menu. BUT REMEMBER, any results not printed will be lost. Also, any results which scroll off the top of the screen will be lost, so it is advisable to enable the printer if more than a screen full of results are expected. The contents of the screen can, of course, be printed at any time by pressing the Prt Sc key. IV AUTOMATIC CALCULATION ~~~~~~~~~~~~~~~~~~~~~~~ This mode works in a similar manner to the manual mode but PRT Calc supplies the inputs. To start this mode, highlight item 4 and press RETURN. PRT Calc will display (and print if enabled) the header and then prompt you for three pieces of information: start, end and interval. For example, If you want the results for all values from 50 to 100 in steps of 0.5 then enter 50 as the start value, 100 as the end and 0.5 as the interval. PRT Calc interprets your input but does not check for out of range values at this stage (see Valid Keyboard Inputs). PRT Calc then asks you to confirm your input and, if OK, it performs all the calculations automatically, displaying (and printing) the results in two columns. It is at this stage that out of range warnings are issued in the same manner as the manual mode. Because of it's automatic nature, and the fact that any results scrolled off the screen will be lost, it is advisable to always enable the printer option before using this mode; assuming, of course, that you have a printer connected). V VALID KEYBOARD INPUTS ~~~~~~~~~~~~~~~~~~~~~~~ PRT Calc is fairly versatile in what inputs it will accept, but not limitless. You can use normal numbers (E.G. 0.0015 or 2300), you can use scientific notation (E.G. 1.5e-3 or 2.3e3), or you can use a suffix letter (E.G. 1.5m or 2.3k). When using a suffix PRT Calc will accept f,p,n,u,m,k,M,G or T. It will even accept the Greek letter æ (mu) if you want to be pedantic! Anything after the first letter is ignored so 2.3k is sufficient for 2.3 kê. The suffix must NOT be placed in the middle of the number, I.E.- 2k3 is NOT valid and will be interpreted as 2k. Commas must NOT be included. 2,300 will be interpreted as 2. Temperature inputs must be in the selected temperature scale. To change the scale use item 7 in the main menu. All inputs must be within the specified range, although inputs just outside the limits will be accepted and a warning displayed. The valid range is displayed in the header. VI SMALL PRINT ~~~~~~~~~~~~~ PRT Calc is intended to be User Supported, which means you are free to use it, copy it and pass it on to anyone on a trial basis. However, if you find it useful then a financial contribution to the author would be in order. Companies should send œ50 but if you are a private individual just send whatever you think the program is worth to you. (Contributors will receive a copy of the latest version of this program and maybe others I happen to have lying around at the time!) There is no printed manual available (you shouldn't need one!) and there is no official after sale support. However, if you are able to get in touch with me then I will give any assistance I can. Suggestions and corrections will be accepted just as enthusiastically as money (well almost!). Roly Williams 22 Morrison Drive Lennoxtown Strathclyde G65 7BA Phone; 0360-31157