A self-balancing nanovolt potentiometric system for thermometry and calorimetry

The principlc of a self-ba la ncing potentiom etric system is d e~cr i bcd . The principle is a pplied to the mo ~ifi.c ati o n of. an ex isting. m anually opera ted t he:mo -~ree, l ow voltage pot en tlOm eter conslstll1 g of Dlesselhorst rll1 g elem ents. The modificatIOn m volves t he addi. ti on of ree.d r elays whi ch ena ble the pot entiom et er voltage to be set by di gital signals. By Il1 cor poratmg a digi tal voltmet er, or an a nalog-to-digital co n ver ter a nd a nanovolt a ml)li fier wi th the m odifi ed potentiom et er, self-bala ncin g of t he poten't iometer m ay be aC. hl.eved through either h ~rdw ar e l.ogic implementation or direct di gital control from a mll1lCOm p uter. T.he resolutIOn of this self-b ala ncing poten t iometri c system for a full scale Il1put of 100 mV I S a bout one to 10 parts in 108. With r eal-time di gital process in g of the data, resolutIOn of about 1 n V or be tter has been achi eved for slowly chan ging in put signals. The over all a ccuracy of the syst em is better than 10 ppm for voltage meas urelTlCn ts a nd abou t 1 ppm for voltage ra ti o or res ist ance measurem ents.