It measures constantly and sends accurate when I do a normal test tube check.
Milwaukee MC120 pH Monitor with Mounting Kit, 0.0 to 14.0 pH, +/-0.2 pH Accuracy, 5.5 to 9.5 pH Set Point https://www.amazon.com/dp/B007Z4HR82/ref=cm_sw_r_cp_apip_mjbgl8j8oOoQG