SO2 upgrade module (0-5000 ppm 1 ppm res.)$1,880.00 For New Testo 352. Testo 340 Call us for a quote Product Model: 0554 2252 SO2 upgrade module (0-5000 ppm 1 ppm res.) quantity Add to cart SKU: 0554 2252 Category: Testo Sensors Parts & Accessories Tag: Testo Sensors Parts & Accessories Description Description For New Testo 352. Testo 340 Related products O2 Sensor 0-21.0 vol%0 out of 5 $93.00 Add to cart NO replacement sensor (0-3000 ppm 0.1 ppm resolution H2 compensated)0 out of 5 $795.00 Add to cart Self service replacement O2 sensor – 325-1 & 325-2 only0 out of 5 $131.00 Add to cart