Add Weld Resistance Demo script

Demo script for measuring battery weld resistance (or any low resistance) using 3706A with 24xx SMU and switch cards.

Instrument_Examples/Series_3706A/DMM_Resistance_w_24xx.tsp

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+--[[
+
+Configures a 3706A with a 3760 in slot 1 and a 3723 in slot 2
+A 24xx graphical SMU sources current into the Output channel of the 3760 card that is routed to channels 3-5 of the 3760 card
+Channels 1-3 of the 3723 measure voltage
+Channel pairings are 3760:3723 - 5:1, 4:2, 3:3
+3 resistors are connected, one for each channel pairing, to create a 4-wire/Kelvin measurement system. 
+A scan of all resistors is executed to measure resistance. 
+Average resistance of each channel is calculated and displayed on the 24xx screen.
+The measurements repeat when OK is pressed on the 24xx screen. 
+This setup is appropriate for measuring very low resistances, as the 24xx can use a higher test current than the 3706A
+
+This script was written to demonstrate battery weld resistance measurements at The Battery Show 2024. 
+
+]]
+
+-- Helper Functions --
+
+-- List all the cards in the 3706A
+function list_cards()
+    for x=1,6 do 
+        print(slot[x].idn)
+    end
+end
+
+-- List all closed channels
+function closed_ch()
+    print(channel.getclose("allslots"))
+end
+
+--Print a buffer
+function printbuff(bufferVar)
+    printbuffer(1, bufferVar.n, bufferVar)
+end
+
+-- Program Functions --
+
+-- Takes a resistor number and averages all readings of that resistor from a buffer that has been used in a scan
+function avg_v(rnum, bufferVar)
+    local sum = 0
+    local count = 1
+    for i = rnum, bufferVar.n, 3 do
+        sum = sum + bufferVar[i]
+        count = count+1
+    end
+    return sum / count
+end
+
+-- Displays values r1-r3 on the connected 24xx SMU, also calls for another scan when OK is pressed. 
+function Report(r1, r2, r3)
+    node[2].display.prompt(
+        node[2].display.BUTTONS_OK,
+        "Average Resistances are:\nWeld 1 ="..string.format("%.3f",r1).." Ohms\nWeld 2 = "..string.format("%.3f",r2).." Ohms\nWeld 3 = "..string.format("%.3f",r3).." Ohms"
+    )
+    node[2].display.waitevent()
+    Scan_Start()
+end
+
+-- Executes the configured scan and calculates average resistances. 
+function Scan_Start()   
+    smu.source.output = 1
+    scan.execute(rb)
+    smu.source.output = 0
+
+    r1 = avg_v(1, rb)/srclvl
+    r2 = avg_v(2, rb)/srclvl
+    r3 = avg_v(3, rb)/srclvl
+
+    channel.open("allslots")
+    Report(r1, r2, r3)
+end
+
+-- Creates a scan. 
+function Scan_Create()
+    scan.reset()
+    -- DMM Configuration
+    dmm.func = "dcvolts"
+    dmm.autodelay = dmm.ON
+    dmm.configure.set("mydcv")
+    -- Always configure DMM settings before configuring the scan. 
+    dmm.setconfig("slot2", "mydcv")
+
+    -- Channel Configurations
+    -- We set a pattern first for readability, but it's not strickly necessary
+    channel.pattern.setimage("1005,2001,2911", "r1")
+    channel.pattern.setimage("1004,2002,2911", "r2")
+    channel.pattern.setimage("1003,2003,2911", "r3")
+
+    -- Scan Configuration
+    -- Here we use the .addimagestep command so multiple channels are closed in a single step.
+    -- You must manually close the backplane channels (x9xx) when using .addimagestep that connect the internal DMM to a channel. 
+    scan.addimagestep("r1", "mydcv")
+    scan.addimagestep("r2", "mydcv")
+    scan.addimagestep("r3", "mydcv")
+    scan.scancount = scancnt
+end
+
+--------------------------------------------------------------------------------------------------
+
+-- Main Program
+-- TSP-Link Init
+tsplink.reset()
+
+-- Globals
+srclvl = 0.5 -- this is the current the SMU will source, it is not measured but it could be. 
+scancnt = 100 -- this is the number of scans that will be used, if you edit this you may also need to edit dmm.makebuffer()
+smu = node[2].smu -- We alias node[2].smu as a helper
+
+-- SMU Configuration
+smu.source.func = smu.FUNC_DC_CURRENT
+smu.source.level = srclvl
+smu.source.vlimit.level = 18
+smu.measure.func = smu.FUNC_DC_CURRENT
+
+-- Buffer Configuration
+rb = dmm.makebuffer(900)
+
+Scan_Create()
+Scan_Start()