An apparatus, comprising: a thermal chamber ; an external heatsink disposed externally to the thermal chamber ; an internal heatsink disposed within the thermal chamber ; one or more thermoelectric devices thermally coupled to the external and internal heatsinks to transfer heat therebetween in response to a pulse-width modulated power signal; a first temperature sensor disposed within the thermal chamber continuously measuring a chamber temperature; a second temperature sensor coupled to the internal heatsink within the thermal chamber continuously measuring temperature at the internal heatsink ; and a feedback control system controlling a duty cycle of the pulse-width modulated power signal in response to a target chamber temperature and real-time temperature measurements produced by the first and second temperature sensors characterised in that the feedback control system includes a chamber feedback control loop in communication with a heatsink feedback control loop , wherein the chamber feedback control loop includes a first controller that calculates the target internal heatsink temperature in response to the target chamber temperature and a real-time temperature measured by the first temperature sensor , and wherein the heatsink feedback control loop includes a second controller , the second controller being in communication with the second temperature sensor as part of the heatsink feedback control loop , the second controller calculating the duty cycle of the pulse-width modulated power signal at which to operate the one or more thermoelectric devices in response to the target internal heatsink temperature received from the chamber feedback control loop and a real-time internal heatsink temperature measured by the second temperature sensor . a thermal chamber ; an external heatsink disposed externally to the thermal chamber ; an internal heatsink disposed within the thermal chamber ; one or more thermoelectric devices thermally coupled to the external and internal heatsinks to transfer heat therebetween in response to a pulse-width modulated power signal; a first temperature sensor disposed within the thermal chamber continuously measuring a chamber temperature; a second temperature sensor coupled to the internal heatsink within the thermal chamber continuously measuring temperature at the internal heatsink ; and a feedback control system controlling a duty cycle of the pulse-width modulated power signal in response to a target chamber temperature and real-time temperature measurements produced by the first and second temperature sensors characterised in that the feedback control system includes a chamber feedback control loop in communication with a heatsink feedback control loop , wherein the chamber feedback control loop includes a first controller that calculates the target internal heatsink temperature in response to the target chamber temperature and a real-time temperature measured by the first temperature sensor , and wherein the heatsink feedback control loop includes a second controller , the second controller being in communication with the second temperature sensor as part of the heatsink feedback control loop , the second controller calculating the duty cycle of the pulse-width modulated power signal at which to operate the one or more thermoelectric devices in response to the target internal heatsink temperature received from the chamber feedback control loop and a real-time internal heatsink temperature measured by the second temperature sensor . <EOS>