Poor mans calorimeter PMC

There yawns a large gap between commercial (micro)calorimeters with maximum vessel volumes of 25, 30 or 100 mL and instruments of many litres for smaller domestic animals. The only exception known to the authors is the Seta-ram GF 108 1-L instrument used in the Leyden group [72]. A low-price solution for an intermediate size calorimeter was found in cooling/warming boxes sold as picnic equipment for less than US 200 [73], They are equipped with a Peltier battery as a heat pump between the inner volume of the box and the environment. In the same way the heat pump can work as a Seebeck heat flow sensor to determine heat production rates inside the box. The inner walls of the box may be additionally covered by copper foil of high thermal conductivity to facilitate heat flow to the sensor. 

In further developments for the investigation of social insects such camping boxes were used for the metabolic observation of whole bumblebee colonies throughout a season [67] and in a differential twin setup with boxes of 24 L for the observation of hornet nests or honeybee winter clusters [75,76], More information about results with these instruments are given below (section 5.5 ). 

Winckler produced a modification of the PMC for aquatic organisms [77]. A camping cooler of 18 L served as an air-bath thermostat for the main calorimetric 

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