When I was updating this page, then coupon price was $16.99 for SINOTIMER SDM009 AC40-300V Rail Single-phase Meter (in Banggood). Just check coupons out (with price alert and history). Do you want to know what the best price is?
SINOTIMER SDM009 AC40-300V Rail Single-phase Digital Voltage Current Frequency Power Factor Electric Multi-function Measuring Instrument – External CT
Latest price update (UTC time):
Banggood ($16.99)
Banggood warehouse is located in China. There is no active coupon in my database right now (for Banggood). Isn’t it too expensive? This price is great, coz it’s the lowest in CouponsFromChina database!
Link: Banggood product page
Price: $16.99
This is the best price ever noted in my database!
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): BGM1TOOLS88, BG20236Tool, BGTOOS729
(there’s a little possibility that old coupon will work)
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Price history and price alert
Price history (for all/most countries) for SINOTIMER SDM009 AC40-300V Rail Single-phase Meter is here.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).