1 EXHIBIT 23 ---------- CONSENT OF INDEPENDENT ACCOUNTANTS ---------------------------------- We hereby consent to the incorporation by reference in the Registration Statement on Form S-8 (No. 33-2496) of Keithley Instruments, Inc. of our report dated November 5, 1999 relating to the financial statements and the financial statement schedule, which appears in this Form 10-K. /s/ PricewaterhouseCoopers LLP Cleveland, Ohio December 21, 1999